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To all, And the prize goes to.... George Badger. My cooling problems are, by now, ledgendary among this group. I was at the shop today reliving the weekend drama. The mechanics were stumped. They gave the radiator the exhaust test which came out negative. So it doesn't look like a head gasket problem. The temp. seems to stay normal at idle, especially with the new electric fan blade the size of a P-51 prop. One guy poked and prodded and concluded that the two bottom hoses collapse when the RPM's are high and the water pump is sucking really hard from the bottom of the radiator. They are both old and easily pinched together. If this is the solution, it will be the relief I've been looking for all these months. George Badger is the only one who actually mentioned checking for a bad hose. I figured if it had a hole in both ends and didn't hold water, it was OK. Guess that's why the radiator hoses are "loaded" with that spring coil, so the won't collapse. It would be interesting to know exactly how much pressure the water pump puts out at different RPM's. One of you guys must have that info on a graph somewhere. I'll report back with the results of this latest solution. - Aloha, Rob XK-140 FHC

Rob: Delighted to hear you may have the answer to the cooling problem. I have to say that over the year and a half of this group, your descriptions of your problems have always aroused the greatest feelings of anxiety and compassion in me. Oh, the suffering! You asked whether anyone had any details about water pressure etc: this might not help much, but here is what Heynes (legend) said to the Institution of Automobile Engineering in 1953 (summary): Water pump runs at 0.9 of engine speed. Caused cavitation at high revs, necessitating a change in impeller design - benefit of competition work evident here. There were some test results at both one pd/in2 and 2 pd/in2 "suction depressions". Graphs also showed pump flow for the revised impeller at 5,400 rpm at between 5 and 45 gallons per minute (depending on pressure difference - between about 10 and 20 psi, and the suction level of either 1 psi or 2 psi). At maximum, the original impeller design had delivered up to 32 gals / min but the new did up to 45 gals / min. He also commented that the absolute water temp made a big difference to water pump delivery, the higher the temp, the lower flow through the pump - e.g. at 20 deg C, about 38 gals/min and for the same pump pressure at 80 deg C there were only about 28 gals/min. Fascinating. This doesn't mean much to me, I must admit. I think I might go back to Dick's question about the 120 number plate angles, for something a little more riveting ... - Regards, John Elmgreen

Rob, 1. Check for water in the oil and for oil in the water also. 2. Pressurize your cooling system using a cooling system tester. If there is a leak you will hear or see it and the pressure reading will change. Check your radiator cap also with the system as it may be bad. 3. Do a compression test. This will tell you if you have a leaky cylinder. 4. Check and/or replace the thermostat. A friend warped his head from this problem. 5. Flush out the radiator. A lot of rust particles and scale end up in the radiator. This clogs the cooling passages. 6. Check for old and collapsing hoses. Check the bottom hose by the damper closely as I have seen this hose rub against the damper and start leaking. A friend destroyed his new rebuilt XK120 motor that way. A 120 is special in that the temp sensor is on the radiator-not on the motor! He thought he was running cool till he stopped. The bearings melted and the head warped beyond usable. - Cleo Bay, XK120, XK140

I'm pretty certain the temp sender on the 120 is on the engine side of the thermostat, where it should be, though the thermostat housing is mounted on the radiator. - George Bagder

To all: All of you list members must be as tired of my cooling problems as I am. The good news is the solution must be getting closer. If the vacuum thing on the side of the distributer is inop. can that cause overheating? If so, would the problem be agrivated at sustained high speed? If so, whos got a neat way to trouble shoot the diaphram, the advance or whatever else might contribute to the heating problem caused by the spark advance/ vacuum problem? I sort of ruled this possibility out earlier because the engine runs well. There is a little hesitation on acceleration but it smooths out. Getting desperate. Water temp was off scale tonight during a nice evening drive. Thanks in advance for any help. - Aloha, Rob XK-140 FHC

Yes, this is a problem. I've a V12 HE, so the numbers will be different, but on the V12 advance is set to 18C at 3000rpm with the vacuum line disconnected. When the vacuum line is re-connected the timing gets out of the scale. When I last set my timing (actually my wife did rev up the engine as I was laying under the car stareing at the crank pulley) it was hard to rev the engine up from idle. I would think that you most certainly have a problem if the vacuum advance is not working which will cause overheating. Sorry if this does not directly apply to your engine. Kind regards. - Matthias Fouquet-Lapa

Rob, A modest suggestion: Whilst cleaning and cataloguing parts and parts for what hopefully one of these days will be a running 140 instead of the worlds largest car kit, I came across the copper vacuum connection pipe. Attempting to blow through it only elevated my own blood pressure, so into the lacquer thinner it went. After a few days I could finally pull a pipe cleaner through it and get 50 years of black sludge and scum scraped off the walls. Since the ID is less than a 1/16" even a small obstacle (crud) will impede, if not the total flow, certainly the response. Might this be a small part of your challenge. Best wishes. - Klaus Nielsen

ROB, On older engines made before the Government found another way to protect us from ourselves (ie., smog equipment on engines, etc.), the vac. advance unit won't have a direct effect on engine running temperature. Having said that, probably it makes a difference when the engine is operated under a load. On later engines, with a myriad of electronic saviors, it probably would but only because it affects other areas of the smog system. The easiest way to test the vac adv unit is to apply vacuum to it (a portable vacuum pump, or just suck on the thing) with the distributor cap removed to see if the plate the points mount to moves. It probably won't, because probably the diaphragm is bad. Especially after 40+ years. XKs Unlimited, for one, has new vacuum advance units available. As is usual, not for cheap (about a hundred US bucks). One may also simply eliminate the problem by using an aftermarket distributor that uses mechanical advance only. I just replace the thing (vacuum advance unit) every 10 to 12 years to minimize expense. - Mike Plechaty

Now this is a point I've always wondered about...Seems to me that the vacuum to the vacuum advance drops on acceleration, thus retarding slightly under load. Every time I follow the hoses and scratch my head I get a different answer on that one. - Jim Warren

Hey Rob, your cooling problem and your continious questions are really getting a pain in the backside. I tell you why a feel like that: Nearly two months ago I offered you a bet, that "the thing next to the distributor", as you call it, is the cause of your cooling problem. I was pretty sure and I still am. Now you show up with the same question which I and some others of the group allready had commented on weeks ago. Are you just bouncing questions at us, or are you sometimes reading the answers as well? - Arno Wahl

Here's the missing piece of information. The vacuum in the intake manifold certainly drops on acceleration, but that is not where the distributor vacuum advance is connected. The vacuum advance is connected to the carburetor throat behind the throttle butterfly. When the butterfly is closed, it effectively isolates the distributor advance unit from the intake manifold vacuum, so no spark advance takes place. When the throttle is opened, manifold vacuum is introduced into the vacuum advance mechanism and the diaphragm is pulled against its return spring, causing the distributor to advance. - Mike Eck, '51 XK120 OTS, '62 3.8 MKII

Rob, In regards to your heating problem,internal combustion engines run with the timing retarded during idle/ low RPM,and (in theory) the timing advances as the RPMs increase. The timing is advanced by two means; by the vacuum advance (first) when the throttle is suddenly depressed, and then, as the engine builds up speed, by the mechanical advance. The mechanical advance willwork without the vacuum advance, and vice versa. They each serve two different functions. When the throttle is suddenly opened, the ignition needs to be advanced to prevent the engine from "bogging down " or "loading". There are more technical terms for what is happening, but from the drivers seat you would feel the car "stumble" or hesitate before it responds to your foot on the throttle. This is the only time the vacuum advance comes into play (when the throttle is rapidly depressed). Once the engine begins to pick up speed the mechanical advance takes over. The higher the RPM (in theory) the more the advance, up to a preset limit. I say in theory because weakened springs, broken counterweights, rusted shafts, etc. will effect the advance curve of the distributor. Now to your problem. Checking the vacuum advance can be done with a vacuum pump checker (this hand held unit "pumps" the air out of the vacuum advance unit and checks for leaks). These are available at the auto parts houses, I think about $20. This will tell you if the vacuum advance unit needs to be replaced. Next you want to make sure the mechanical advance works without obstruction. Check that the springs are not stretched and that the weights can freely turn on the posts. After having checked all this go back and re-time your engine. If either of these were faulty they would have effected your engine timing. Best of Luck! - Bill Fair 140 FHC

I think Jim is right - the vacuum is present with a feathered throttle and that advances the timing. The rotor is going counterclockwise and the vacuum rotates the plate clockwise thus bringing the points into earlier contact with the cam. The lack of vacuum with the throttle open allows the spring in the mechanism to retard the timing under acceleration. - Bruce Cunningham, '53 XK120 OTS

Rob, Regarding your continuing overheating problems, another possibility that I don't think was mentioned yet is: a blockage or restriction in the muffler or exhaust pipes. An intermitent ( A rusted flap of metal in a muffler can act like a butterfly valve) blockage or partial blockage in the exhaust can hold in a lot of heat. Perhaps your car has several "cooling critical" components that are operating at 70% but in combination they bedevil you. For instance with the timing running a little retarded, and the exhaust partially blocked, and radiator partially blocked, these all add up to a cooling system failure that defies the standard fixes. The only thing you can do is check every component or system that has an effect on the engine cooling again. If you have a competent shop doing this for you this will cost a lot of money. The solution is not finding someone who moonlights as a inexpensive mechanic, sometimes this can work but often times it just leads to mechanicitis (translation the car gets worse but it didn't cost you a whole lot). We in the northern hemishere are settled in for the long winter, so I'm sure if you want to do all the work yourself we can help walk you through the repair process. On the other hand you could sponser a contest (The help Rob fix his overheating problems contest) the winner gets to fix Rob's Jaguar, of coarse this will have to be an two week all expenses paid deal. This might sound expensive,( remember Rob lives in Hawaii) but who knows, it might turn out to be cost effective. Maybe Arno will win! P.S. Note: for the humor- impaired some of the above is tongue in cheek. - Regards, Wray Schelin

To all, I started to keep track of everyone who has offered help regarding my overheating problem. Thats why I settled on "To All". Many thanks to all of you. The distributor came off yesterday and the vacuum is inop. The diaphram must have been solid. Pushing on the adjusting pit seemed to "break" something loose inside the unit. That is the first thing I have found that is actually inoperative during this process of elimination. Arno, I'm sure you will take special interest in this possibility. My local mechanic does not share your opinion and says the vacuum isn't needed at all, and wouldn't cause severe overheating. That the advance can be adjusted to compensate for the vacuum not working. Doing that may cause other problems and isn't the kind of solution I'm looking for. I might add, that this is the same mechanic who can't figure out what is causing the problem. Sam suggested the gauge might me bad. It was rebuilt two years ago by West Valley Electronics in So. California. To check it, I recently took the temp. of the water at the neck of the radiator and compared it to the guage. Both the same. The water is definately getting hot because I can hear it perking inside and the puddle under the car is hard to overlook. A recovery system will be high on the list when I get this thing solved. To head off the next question, the engine gets really hot before it looses the water from the system It has a stock 4# cap and using a higher rated cap won't fix the problem. Just hold in the overheated water longer. Still on the list to check is a possible plugged exhaust pipe, and the most recent suggestion from John, a slipped timing belt resulting from worn teeth. The paper work from the PO rebuild lists two new timimg belts and a new tentioner, but no mention of gears. Worth a look. What I'm worried about is running out of suggestions and still having the problem. Stick with me guys. I get enough heat on this end. - Aloha, Rob XK-140 FHC

Have you tested the water for particles of exhaust? If you have the particles, a head gasket or worse may be your overheat problem. Bubbling or gurgling in the radiator when the engine is running is evidence of air pressure leaking into the water system. - Steve, XK120 OTS

Rob, A couple of things to look at: 1. Dragging brakes. Does the car roll freely? Can cause the motor to work harder. 2. When the cap is off and the water is at temperature, can you see water being pushed from the engine to the radiator. (i.e. a water flow) 3. Are the carbs set too lean? Gray or tan plug color? 4. Try a back flush of the radiator. I have had rust from the block clog a radiator in a very short time period before. Does the car overheat at speed? 50-70MPH? - Cleo Bay, XK120 OTS, XK140 OTS

To all, Have read with interest the ongoing saga of overheating. All answers are correct, but of course which is most correct? In point of fact, what is the real cause? For my 2 pence worth, I suspect a seriously blocked radiator or blocked water passages in the head or block or both. I have encountered similar cooling problems in the past on other vehicles and the really stubborn ones always were interior blockages(engine and/or radiator) (assuming of course, the pump is pumping and other things are correct). All things being correct and normal, the vacuum advance not working will have little or no effect on the cooling. In fact, when I registered an out-of-state 1969 Ford van with 302 V8 in California about 10 years ago, the required smog "fix" was a kit that consisted of two rubber plugs and 2 decals. The installation of the kit required discarding the factory vacuum advance hose and installing the rubber plugs over the nipple on the advance unit and nipple on the vacuum source. The decals were installed on the dash (one English, one in Spanish) to tell the next rocket scientist who smogged the car, that the kit was installed. Sorry to say, but I think you've got some serious blockages. While all the little things suggested to check are meaningful, the type of overheating you describe is way past what is caused by incorrect timing or a bad radiator cap. This suggestion is a real stretch, but since I've done it on a routine basis and I know it works, I'll throw it out on the net and listen for the electronic "oh my Gawds." Years ago while working in commercial refrigeration maintenance, the compressors I worked on (mostly 3 - 10 hp units) that used water-cooled condensers were always subject to cooling problems. Water treatment not withstanding, lime and scale would build in the condensers, the condenser would run too hot and overall efficiency would drop to the point maintenance was required. Not too hard to see the parallels here. The standard fix was to circulate a mild muriatic acid solution through the condenser for a period of time to remove the lime and scale. We used a small rubber-impeller pump with a 1/4 or 1/3 hp motor. Connect input and output lines as required with the suction side in a 5 gal bucket and the discharge side in a like container. In fact we used 3/4 in heater hoses for our connections. Start the pump and run for 30 to 60 minutes. We would run the compressor for short periods to keep the solution warm/hot. It works better and faster. A mild solution of acid did not attack the gaskets or metals in the condenser or cooling system. After the treatment, flush well with fresh water. Maybe a little baking soda to help neutralize the acid. If in doubt about the effectiveness of this process, talk with a commercial refrigeration mechanic who deals with water-cooled condensers. I personally know this process works and would try something similar before pulling apart an otherwise working Jaguar engine. Obviously, caution and common sense are required before undertaking such a process, but I do know Jaguars can drive one to desperation. (It once took me over a month and many special tools and techniques to remove the head from 65 S Type sedan. But that's another story.) - Best of luck, David Sales

My experience with twenty years of operating Jag-u-ars In high ambiant conditions [XJs,XKEs,and for eighteen years an XK 120in Texas] is that under normal conditions of over the road driving, a properly tuned engine in good condition will not overheat.I would look for Cracked block [Had that] warped head,timing and every thing that goes with it.We assume that the coooling system,pump, adiator,hoses,etc are up to snuff. Overall good engine condition is paramount. Good luck. - Miles Hawk

To all, I do not recall whether the questions of worn impeller and/or insufficient waterflow have been asked. How much is necessary and is there a sensible way to verify the flowrate without taking the pump off the engine. - Klaus Nielsen

David, Did you have personal experience with Hydrocloric (Muriatic) acid washing of aluminum components? Since this is what chemists call an irrevesible process and not knowing precisely the composition of the engine alloys, I would borrow a scrap head or block and test the method before subjecting my "good one" to a new witches brew. Chances are it will work,but........Regards. - Klaus Nielsen

I thought oxalic acid was the preferred radiator flush. - Mike Eck

Yes. If the there is a water flow problem, the radiator is still cooling the water IN in the radiator at the normal rate, and so the temperature at the bottom hose should be cooler than normal. Does anyone know the normal temperature drop from top to bottom of the radiator on a correctly functioning XK system with the engine working hard? This might be useful information for Bill and others. - Regards, Mike Morrin

After removing the freeze plugs on some XK engines I have noted not only large amounts of rust in a dry dusty form but I have removed clumps of muck and mud at the base of the cylinders. I could take my fingers and remove hunks of the mud! I was astounded to see so much buildup which was probably attritutable to poor maintenance. So, the muck and mud displaced water in the blocks of some of these engines. Since the temperature of the water in the block is primarily dependent upon water convection, it is amazing that a reasonable operating temperature is maintained as well as it is. Definitely the build up of the solid crud I've noticed doesn't help an already marginal problem. If your engine has not been properly maintained nor boiled out during a rebuild, you might be surprised at the amount of contamination in the cylinder block. I'm not suggesting that you run for the garden hose or drive out the freeze plugs for a look-see, but.... - Bob Oates

David, Thanks for your suggestion. The same acid flush idea was suggested by a mechanic at XK's Unlimited just last month. When I mentioned it to a second mechanic, also working at the XK's Unlimited shop, he was horrified at the thought of putting even a mild acid inside an engine. Talk about being caught in the middle. His concern was that it would eat everything it touched and result in leaks from every seam. One thing I welcome is lots of ideas, but, deciding which ones to use can be frustrating. I don't want to cause more problems than I'm fixing. This idea does sound extreme. It also sounds like it is very effective and possibly worth trying. My question is, what is the ratio of acid to water to get a "mild" solution. My radiator is new and has been flushed frequently. I know it is clean and wouldn't want to damage it with an unnecessary acid flush. Also, should the thermostat be left in during the flush? Maybe it would be damaged. I just called two radiator shops. They both gave a thumbs down on the idea. One said it is against the law to dump it out and the damage it could do to the system would be uncontrolable. The other shop had never heard of the process and also thought it would be asking for trouble. I might also ad that neither of them had experience with trying it. I will call a refridgeration guy to get a third opinion (forth including yours). I've had the head checked for warping and leaks with negative results. If I do decide to do this, I'd like to keep the radiator out of the "loop" and use a large bucket for the supply. Also, put the discharge hose back into the same bucket so the engine water pump is circulating the same solution without going through the radiator. One guy said the freeze plugs would probably "melt". I think the correct mixture is real important to avoid all these problems. Have you ever heard of someone trying this on a car engine? Thanks again for your help. Aloha, Rob XK-140 FHC

A similar condition is common with tankless coil or "instaneous" water heaters in boilers. These are copper heat exchanger coils that reside in the boiler water. Potable water is drawn through and heated for DHW use. The heating causes calcium compounds to precipitate and accrete on the inside of the coil resulting in a sclerosis of sorts. Some contractors will flush the coil with acid to enhance heat exchange, some won't because of the potential for making a hole and cross-contamination of the potable water with boiler water. The flush may work great for scaling in the radiator tubes, but it seems that to be effective for a major blockage in the head it may have to be present for such a long time that holes in the radiator may result. I agree with the suggestion to try it on a sample of all the materials first. - Sam Bell

Cleo, The car does roll free and easy. The thermostat is a new 160 degree that has been checked twice recently and cross checked with the temp. guage. They agreed. The radiator has been flushed many times. The engine has been tuned but the cam timing chains have not been checked. The water can be seen moving across the top of the radiator after the thermostat opens. The temp. goes up to over 100 after a stop and go ride of only 15 minutes and also on the freeway at high speed. My electric fan has had no positive effect on cooling. Replacing the hoses dresses up the engine but had no cooling effect. - Thanks Aloha, Rob XK-140

Bob, Why didn,t I think of that? You are right on the mark with the rust sludge build up. At my grandfathers one of the grudge jobs that I was assigned was cleaning out the water jackets on J Duesenbergs. They have finned aluminum water jacket cover plates, on both sides of the motor. If you removed the four plates you would expose the water jacket, most of the time I would find the whole jacket packed solid with rust sludge. I would flush out the 30+ years accumulation with a steam cleaning wand. The sludge would be thicker towards the rear of the engine. Maybe Rob could pop out the least difficult to remove freeze plug, and make an assessment. A pressure washer with all the freeze plugs removed would do wonders. - Regards, Wray Schelin

Rob.From this statement can I draw the conclusion that the top tank has not been removed from the radiator and the water passages have not been physically checked. if you haven't done this to date I strongly urge to make this the next step, as in some cases the flushing will not remove the sludge build up ,I owned a radiator repair shop for several years and have found this often happened. - Regards, Don Tracey, 58 xk150 ots

Hey Rob, I am glad that you took my rough words as a man and did not take it personal. It wasn't meant like that. My experience with Jaguar overheating was that nearly everybody at pub bars said, that old Jags have to drip and burn oil and that they were built to overheat. I doubted that, because when everything is set right on a Jag 6 cylinder XK engine and the engine runs smooths, no water leakage no drop in compression ratio the engine should run forwever at moderate water temperatures without the help of electirc fans and other gimmicks. I prooved that opinion for many years, until one day, when my temperature needle tried to compete with the oilpressure one. I had never seen it moving up so high at the gauge. First I checked the radiator and had it cleaned Next ignition timing I did not forget to tinker with the carbs (totally wrong, but a screwdriver is allways within reach) Finally I took the vacuum pipe off at the carb and sucked on it, while watching the the ign point backplate. What happened with this Heath Robinson test: I could breath through the pipe. The backplate did not move to advance. That meant, the goat leather membrane in "the little thing next to the distributor" had given up. Long story short: I replaced the vacuum box, and the cat was cured. The needle never went that high again at the Smith gauge. Aloha to Hawaii. - Arno Wahl

Rob. I think you have looked into all the things that can cause overheating except some sort of blockage in the block or head. On my XK140 a few years after I bought it I discovered a seeping frost plug. On removal it had an almost solid wall of crud behind it and without adequate coolant circulation the plug was rusting. I removed some of the solid stuff and out oozed about a quart of a porridge like slop. I think it was some residue from some "stop leak" stuff. After mucking about in the jacket with pieces of wire and a small diameter bottle brush I removed about another quart of crud. The engine ran a bit cooler after although it hadn't overheated before. Possibly the removal of at least 1 frost plug might give you some indication if a blockage is there. Also I think if it is possible to remove the 3 threaded plugs in the spark plug valley (I haven't ever removed these but I bet someone on this list has) these may give access to the jacket and a wire (coat hanger size) may be able to be used to push out any blockage into the block and flushed out of the system. Best of luck. - Bill, 1955 XK140 OTS

Don, Thanks for the help.The radiator is new (6 months ago) so there is not much to flush out. From sheer frustration, I give it a flushing every time I get "into" the system to do something. It is the cleanest radiator in Hawaii. It is also a modern design core with lots more passages and an extremely efficient air flow which is accelerated by the 12 inch electric fan mounted directly to the back of the core. And yes, it is spinning the correct direction. Bill, I have removed one of the core plugs. The center one behind the exhaust manifold. Only a little sediment and scaling were found. I used a high pressure hose to flush it out through the opening in the front of the engine where the water pump was removed. The suggestion of removing the three threaded plugs in the spark plug valley is a new one, and a good one. Also, a lot easier than removing the entire head. If anyone reads this, and has experience with this part of the anatomy, please advise ASAP. Thanks. Arno, the vacuum advance unit is bad. The membrane was shot and on close inspection, I actually found a small hole rusted through the side of the housing itself. I found no number on the part. Just the word "British" stamped into the side. With all the other stuff I've checked and replaced, I expect the car to run as cool as the wind chill here today; about 75 F. Our reward for beating this overheating thing will be an early morning ride through a new, one mile long tunnel that is opening soon. You will all hear the tail pipes roar. - Aloha, Rob XK-140 FHC

Rob, Cleo Bay has a good idea about checking the spark plug colors. Also, how fast does the water move across the radiator? At a fast idle, my pump froths the water due to the high velocity. Since you have now checked the block as Bill suggested, and your thermostat is good, if you see very slow movement of water, the timing cover or water pump impeller could be pitted or worn. Did you ever do an exhaust gas test of the water?? Since you now know that your vacuum advance is not working, have you checked that the centrifugal advance weights underneath the breaker weights are freely moving? A timing light showing the correct advance must be done to verify that. If you don't have a blown headgasket, retarded timing, a soft bottom hose that is collapsing or poor water flow, the answer to your problem will be very interesting. That engine has to be getting very warm to be boiling the water so fast, especially with an electric fan on the radiator. -

Rob: Am reading with interest your overheating. My xk140mc ots had the same problem. Went through the same diagnostics and even had a custom built aluminum radiator built. I usually ran ok heat wise until I slowed down, then the heat would build up and never really go down. Subsequent slow dows were the same and the heat needle stayed close to 95-100 all the time. Always cause for stress. The new radiator worked great but didn't cure the overheating. CURE: Check the cam timing with tools on both cams at the same time. It's the only way to be sure they are exactly timed. I tried to time them separately but found it was not exactly right. My intake cam was about 2 or 3 small teeth out. Retimed both cams and it works great. I took off the fan blade and now use an electric fan set at 180 degrees. From startup I can drive road speed and the fan won't come on. No stress now. Good luck. - Robert H. W. Cathey

I'm not following the crowd. I think you have a serious engine problem. I bet if you did a cooling system pressure test, I'll bet that you would find a pressure drop. This would mean a head gasket or cracked head (my bet). Plug colors might reveal this also becasue the steam created can really make hose little guys look good. Are you sure it is not puffing white at start up..just a little. john shuck..beijing

Dear Sir, In 1969 my father pit crewed for Billy Wolf who raced "E" production with a spitfire. We took the thermostat out and found that the engine would overheat without some regulation of the coolant because the coolant would run through the radiator so fast that it did not have time to cool. There was a formula car driver in Fort Meyers Florida that sold us a sleeve with 3 holes in it to restrict the flow just enough to let the radiator do its job. The moral of the story is, maybe the thermostat is stuck open not closed and I believe that there needs to be something to control the flow. - E.W. Blake

Dear Sir, Reference only: My head gasket blew and one thing to look for but not necessarily conclusive is the color of your oil. If a certain area of the gasket leaks it is possible for the water to get in the oil and this in turn will turn the oil muddy or milky looking. Just a note. - E.W. Blake

May I put my 2 cents worth in here to endorse the probability above. When I tore my MK VII engine down, the vanes on the pump impellor looked like razor blades and the timing case cover was somewhat pitted. All this leads to internal pump losses, not much help when you may be dealing with the possibility of a partial blockage in the water cooling passages. Try pulling the pump off and putting a lump of modeling clay in the housing and squash it with the pump to see what your pump clearances really look like but don't leave it in there though! One more place to check could be the induction manifold, proper water flow through the cylinder head is dependent upon correct flow through this lump you hang your carbs on. Bash those great big frost plugs out at each end and let's all have a cyber-peek inside. Oh Boy! this is getting to be more fun than the "Great Dill Pepper Jar Caper" "Allothere" - John Morgan

I did run without a thermostat for a while and things got as hot as ever. Put in a new 160 degree one from XK's Unlimited(couldn't be installed backwards) and that had no effect. No white smoke on start up. Just had the oil changed and it was normal. As we continue to trouble shoot this problem, keep in mind that this is a 1959 MK1 engine in my 1955 140 body. There are a couple of differences from the correct engine, but hot is hot, and the problems are shared equally. Does anyone else think it is worth while removing the HEAD core plugs to clean the passages, or is there too little access? ( one BLOCK core plug has already been removed with no visual evidence of any contamination.)The thermostat has been checked twice and operates correctly. I have already removed the water manifold above the intake on the right side; the one that collects water from the head and moves it forward to the radiator (thermostat open) or directly to the pump (thermostat closed), and found no evidence of any contamination. This seems like it would be pretty representative of what a visual inspection through the HEAD core plugs would reveal. I just thought of another solution. I received, for free, a couple of years ago, a 1967 MK2 engine. (it was my house or the dump) It is a 3.8 and would be a great upgrade to the 140. The engine I have isn't original so nothing lost there. A nice, fresh, newly rebuilt powerplant would sure give us all a lot more free time and more time to drive. Windchill plunged all the way to the low 70's today. Almost time to start driving with shoes and socks on. Thanks to everyone. I'll keep trying all the suggestions. - Aloha, Rob XK-140 FHC

A couple of quick ones to try: 1. Check your damper cone to see if the wooddruff key is sheared. This can be checked either by pulling off the front damper or initially with a timing light. If the timing is moving about while running, this would be good indication of bad wooddruff key. 2. Check the bearings in the generator. Check to see if there is any resistance to turning. This can cause the belt to slip. Another thing to try is to disconnect the small wire on the generator and drive the car a short distance. It won't be charging, but you can see if there is any effect on the cooling system. - Cleo Bay, XK120, XK140

Note : I saw a thermostat in XK -Unlimited called a Superstat that is a by pass thermostat that insures all water will pass through the radiator. From what I understand, with a regular thermostat, 20 percent of the water never passes through the radiator. ( page 60) - E.W. Blake

I was surprised that the comment about the type of thermostat was not mentioned earlier (thanks to E. Blake). I was getting ready to do this but he summed it up very well. Too add my words to the overheating problem Rob is enduring, it is my understanding that the cooling system of the XK engine is marginal at the best. So, as the engine wears and ages the margin between normal operating temperature and overheating narrows. Nothing profound about this. But one can forstall this problem with the correct type of thermostat. The original thermostats had a small, ball-shaped valve that controlled the water/antifreeze mix circulating through the bypass portion of the cooling system. When cold and in a closed position, all of the mix circulated through the system. When open, a small volume of water circulated through the bypass portion and not through the radiator. It doesn't take a genius to figure out that the mix circulating through the bypass would only get hotter! So how hot would it get the block and the rest of the engine? You guess. If you examine one of these thermostats you notice that the hole is not much larger than pencil lead. When Dave Laughton, Coventry Classics, Mike Evans, XKs Unlimited, and Tom at British Auto (US) told me about this, I was skeptical that such a small feature could make such a large difference. And I was also skeptical when I was told that this special thermostat was more costly (about $35). Anyway, I have been convinced in using the "bypass" thermostat and fortunately have had good success to date. So, the price is nothing when compared to the frustrations of tracing down an overheating problem. - Bob Oates

Bob, Thanks for your reply. I did remove the center freeze plug on the left side, behind the exhaust manifold. There was only a little sediment at the bottom of the water way. With the plug out, the pump off, the upper water manifold off above the intake manifold (its a MK1 engine) and the exhaust manifold off, I proceeded to use a high pressure hose to flush out the engine from every possible direction. I am certain there is no more loose crud inside. A visual inspection revealed only a very little scaling around the cylinders. Nothing that I would consider a problem. The longer this problem goes on, the more I suspect there is a blockage in the head or other small passage. Removing the head is getting to be a definate possibility. - Aloha, Rob XK-140 FHC

Rob: Been trying to get through for a few weeks now. My xk140mc ots was running hot also. Recored the radiator-a little cooler but still ran very hot. Had a custom aluminum radiator built. Beautiful, and a little cooler but still overheated. I ran all the tests everyone suggests and one more. I helped build the c-type engine and just knew the cams were perfectly timed. Well guess what. The intake cam was about 3 teeth off. Be sure you use two gauges and simultaneously time the cams. Once I was in time I really enjoy the aluminum radiator as this cat is the coolest in town. Good luck and us all know the results. - Robert H. W. Cathey

John Elmgreen: Very funny. No objection from this garage. Also, don't know if I ever passed on the number of my "extra" engine. Its a 3.8L # LE 1412-9. Book says its a 1967 MK2. Does that agree with your records? Bob Oates: Installing a nice new Superstat Thermostat from XK's was the first thing I did. Robert Cathey: I also had a new alumunum radiator built. It didn't leak like the old one, but the engine still overheats. I will definitely check the cam timing; both at the same time. That will be the first thing after the long Thanksgiving weekend. Family is going to So. Calif. for a few days. The volcano is beginning to act up. Rob: Checked my distributor number on the web site. I have #40199E. Records say it is for an XK- 120 8:1 CR. I have it installed on a 3.4 MK1 8:1 CR. Also have it fitted with a positive ground, electronic ignition system. The new vacuum advance is in the mail and the dist. will get another good cleaning while it is out of the car. The weights operate fine. Also have a high energy coil that puts out a great spark. No choke of any kind needed here. Not even installed. Starts on the first turn. - Aloha, Rob XK-140 FHC

I mentioned the problem of the Hawaiian 140 Volcano at an XK meeting here today, and got another suggestion from restorer Gavin King. I hope I get this right! (1) you can no longer get anywhere the correct thermostats for XKs (I think he said they do not have some lip or other) (2) that lip is part of the control of the water flow through to the bypass system (3) if you use the wrong thermostat, most of the water will always go to the bypass system and not be cooled (4) you therefore need to (I think permanently) block off the bypass and make sure the water goes through the radiator. Some of you guys will work out whether my passing on secondhand of this suggestion makes sense or not. I had thermostat problems with my 120, as they kept malfunctioning and blowing core plugs. I can by the way offer to solve Rob's overheating problem: the gauge in the 150 now records no more than 55 deg C, so that should keep Rob happy. Rob, want to make me an offer for the gauge? Guaranteed you'll never show over 55 deg again. - Regards, John Elmgreen

Note that the original type XK radiator is a "V-Cell" that does not have the typical tubes that can be "rodded" out. Once a V-cell becomes corroded inside no flushing will help. I would suggest that a new radiator core will solve your overheating problems. - Jamie

I think the thermostat of the correct configuration is now available. And if someone is blowing core plugs it may be because the core plugs are week, or the radiator cap is not working as it should. What pound pressure cap should be on the 54' XK-120?? by the way. Can I use one from the local auto supply? or is it something special? - Edgar Blake

Hi Edgar & all -- system is 4 lbs., so cap should be 4 lbs. -- neck is larger than most U.S. cars -- try a truck supply house. - Larry Martz

David Laughton of Coventry Classic Cars told me exactly the same thing. He recommended not plugging the by pass completely, but leaving a 3mm hole so that tere would be some flow in the bypass at all times. - Neville Laing

Greetings, Cooled off some during a short mainland visit. Back now and ready to try the last few suggestions. Jon Spence: The guage has been checked and is calibrated correctly. High temp. indication cross-checks with puddle of coolant under car. Jamie: I replaced the radiator when the old one started leaking. So. it's a nice new, modern alum. type with a large electric fan mounted on back. John Elmgreen: Thanks for the offer. My water temp guage indication is usually at 55 now, trouble is, its in the oil pressure half of the guage. Nevill and Bob Oates: I already have a new "Superstat" type thermostat from XK's. Its been checked and rechecked both in and out of the car to make sure it opens at the right temp. and also that there is enough flow into the radiator. It doesn't "froth" across the top of the radiator, but it does move. The car should be back running today with the new vacuum. (keep your fingers crossed Arno) Next will be the check of both timing chains and cams to make sure it is set correctly. Heck, I'll do that anyway. - Aloha, Rob XK-140

4 PSI and must have the correct depth of seal into the filler spout of the rad. No readily avaiable at regular parts outlets. - George Badger

To all, Thanks to everyone for your continued help. I realize my overheating problem has lost a lot of the interest it generated in the beginning. Unfortunately, it still isn't solved. The vacuum advance unit I received was for a different type of dist. The correct one is on the way. Discovered I've got a 120 distributor on my MK1 engine in my XK-140. I checked the cam timing on both sides at the same time, and they were exactly correct; not even one tooth off. While lining up the rotor, the #6 piston and the reference line on the flywheel, I discovered the flywheel was 180 degrees off, and the distributor was wired with the #6 ignition wire to the rear instead of the front. The mechanic who installed the electronic ignition messed this up. I can hear my Dad's advice ringing in my ears, "if you want it done right, do it yourself." Thats all corrected now. I'm going to ask one more question of the group before removing the head in the search for the overheating problem. It has to do with the plumbing between the heater and the cooling system. Remember, this is a MK1 engine if it makes any difference. On the side of the water pump, there is a little hose that carries hot water to the valve that controls the flow through the heater core. Irregardless of whether the valve is open or closed, the coolant circulates from the pump, through this valve and the heater core, if the heater is on, and then through the upper water manifold that sits on top of the intake manifold. From here it goes forward to the radiator via the thermostat or the pump by way of the bypass. If this logic is incorrect, please let me know because my question is based on this understanding of the system. My heater core leaked badly. In this climate, a heater is the last thing I'm going to repair. so I removed both it and the ON-OFF valve, and "looped" the hose from the pump directly into the rear end of the upper water manifold. Here is the question. Could this "alternate routing" of the heater hose have any affect on cooling. Would it make any difference if I eliminated this hose completely and plugged the outlet from the pump and the inlet at the rear of the manifold? I'm thinking that possibly the flow through this hose helps "push" the water through the manifold where the pump pressure would be the lowest. I realize this is really getting desperate for answers. But that's what I've become. Any thoughts would be appreciated. The end of the year is bearing down, time is running out, and a new one mile long tunnel opens this Friday. Think of the sounds possible all alone inside a mile long tunnel. - Aloha,Rob XK-140 FHC

Rob; Am I correct in reading that your flywheel is 180* off. Have you had a new clutch put in lately or has it been this way all along? I can tell you from experience that a flywheel out 180* can cause your overheating. - Skip Smith

There are many reasons for an engine to overheat. Although I do not agree with your logic: The hot water comes from the water pipe on top of the inlet manifold , goes through the tap, then the heater then to the water pump. If the tap is closed there is no movement of water in the pipes and heater. I do not think that the water pipes to and from the heater change anything It it is easy to check by disconnecting or plugging them. Assuming that ignition and distribution are correctly timed, before removing the head I would also: remove the thermostat; plug the water pipe between water pump and thermostat ( by-pass); check the flow of water in the radiator, check the radiator cap or fit one with stronger spring; check the cylinder head gasket ( bubbles in radiator ?) - Regards, Michel Gosset

Skip, For those among us who have less experience with these problems, could you elaborate a bit on.....why the 180 degree error may cause overheating. Thanks - Klaus Nielsen

Yes, I believe it reverses the compression/exhaust stroke cycle so that the car accelerates when you lift off the gas. %=) Jim Warren

Rob, Plug the heater lines. If I remember correctly, water going through the heater would not go through the radiator and not be cooled. This should not be the full cause of your overheating, but would contribute. - Cleo Bay, XK120 OTS, XK140 OTS

Rob, Seems that you have checked just about everything that can cause overheating. The out of phase problem between the block and head I have solved 2 different ways and both were successful and no overheating. (1) Change the cap wiring. (2) Reverse the spade connector on the bottom of the distributor to move it 180 deg. The flywheel can't be put on 180 deg. out. The dowel pins won't let it happen. I tried it when I had a bad ring gear. Try doing a pressure test on the rad when the engine is hot. Don't do it cold. As you may have a compression leak or head gasket leak that opens up only when the engine is hot. Crank the engine over during the pressure test. Another quick check is the odour of the exhaust when the engine is hot. If it smells like burnt sugar it is antifreeze in the exhaust. Your pattern of overheating sounds like problems with the old flat head Ford engines and this usually occured after overheating once for other reasons and it was traced to hairline cracks in the exhaust ports. If you remove the head there is an aluminum crack check proceedure used on aircraft parts. I have the U.S. phone number for a supplier, but call some of your local aircraft shops. You will need a 'black light' to use this material. - Bill, 1955 xk140 ots

Klaus; I just had this happen to me about two months ago when I bought a car at auction that was runing a little rough but would clear up at higher RPM's, however the temp started going up. No big deal I thought probally just plugs, wire or rotor/cap. So I replaced all. No help, next to flywheel sensor and some other stuff. Same results. As I stood under the car doing a oil change I happened to notice that the the trans bolts and nuts had some shine to them as though they had been removed recently. So I went through some of the papers in the car and found the previous owners name and address. I called and ask if they had the car serviced recently. That is when I found out that the clutch had just been replaced and when they got the car back it just did not run quite the same so they traded the car in. After finding this out I checked the timing and it was off 13*. Well to make a long story short if your flywheel is in 180* out you can't set the time. As others have said regarding the vacume advance this will cause overheating and rough run at low rpm. - Skip Smith

Skip, Thanks...that clears that bit of cobweb away. - Klaus Nielsen

Skip, XK engines are not timed at the flywheel. - George Badger

For the record, the product that is used to detect cracks in aluminum is called Die Penetrant. We used it @ Rockwell when we built the B1B and the Space Shuttle parts. I am not sure where to get it but I will have to find a source soon because I have to check my head as well. - Edgar Blake

Bruce, Give me a little credit. I know #6 cyl. is in the front of the car. Skip, Thanks for the flywheel / timing lesson. On a 3.4 MK1 engine, how many teeth equal the correct advance to set the timing? Michel Gosset, I have checked all you suggested. Thanks for the heater plumbing. I had the flow going the other way. Bill, I fixed the flywheel problem the same way you did; by reversing the ignition leads to the correct sequence beginning at the front (#6) and following the firing order all the way around the cap. I didn't know about the idiot proofing pins in the flywheel. I work for Aloha Airlines in Honolulu. They have all the latest gear for finding cracks in metal. All I need now is a sympathetic airplane/car enthusiast who work the night shift. Good idea. To all, Regarding timing. Lots of theories floating around. Most common is: if it sounds good, and runs OK, it timed right. Is there more to this than meets the ear? Anyone can comment on the "how many teeth equal the correct advance to time an engine statically" question. Its a 3.4 8:1CR from a MK1 with a 120 Distributor with an electronic ignition system. Wouldn't it be something if all these unrelated parts were what is causing the overheating. I know it isn't because it has worked well in the past. One book I have says that XK heads rarely stick during removal. Just the fact that sticking, and XK is mentioned in the same sentence makes me think I'm in for a whole new lesson in disassembly. - Aloha, Rob XK-140 FHC

When I was a mechanic and for all of my cars I have timed them "by ear". At idle, I initially adjust the timing for a combination of smooth running and maximum idle rpm. Under running conditions, if it pings a little under acceleration, I retard the timing a bit until the ping doesn't happen. The 300SL, I believe, has a knob on the dash for adjusting timing while driving and I thing there are other cars with similar controls. I tried timing the XK according to the 5 teeth (I think) before TDC and it just didn't work as well as doing it by ear. I honestly don't know where the timing is set now but I do know that it starts and runs beautifully. - Bruce Cunningham, '53 XK120 OTS

Correction - I just checked the manual - the 5 degrees before TDC for #6 is "two flywheel teeth approximate" between the arow on the flywheel and the arrow on the block. The final instruction on timing is "Make final ignition setting on road test" - an apparent confirmation that it is ultimately a "trial and error" process. - Bruce Cunningham

Rob C, I just had another thought. On my 120, the timing mark is by a hole in the upper left of the bell housing in line with the dipstick. I vaguely remember seeing in a manual that on a Mark 1 the timing mark hole is on the bottom of the bell housing. Is there any chance you have a Mark 1 flywheel and a 140 or other bell housing, i.e. that the two are not a matched set? - Rob Reilly

What do you say to an En Masse Trip to Hawaii (Jan /Feb??) for all the members of this list sos we can all just pitch in and fix Robs overheating problem?? With everyone there, I feel certain we could fix the darn thing.... Im up for the sacrifice....what about the rest of you????????? - Dave Drenzek

I have never been there so I 'm Ready Ha! ha! Just kidding Rob. - E.W.Blake

It has been suggested that everyone on this list converge on my garage in one collective effort to find the reason to my overheating. I'm sure the suggestion was made in the same good naturedly spirit as other comments a couple of weeks ago. When you think about the idea, it makes a lot of sense. We can all meet each other. All of you guys get to have a great Hawaiian vacation working on an old car and when you get home, there won't be a ton of digests to catch up on, especially from me whinning about my overheating. So, in the continuing spirit of the Season and in the interest of British cars everywhere, you are all invited to my house. Call from the airport and I'll pick you up. Stay here for as long as you want, until the car is fixed, or you run out of ideas. The weather is great. I just filled the Bar-B-Q tank with gas. And besides, it would be a lot of fun. What more of a reason do you need. One day we can all go for a tour and see the other XK's that are hiding around the island. You all know how to reach me. Thanks for the offer. Melekalikimaka, and Aloha, Rob with the hottest 140 in the islands

I've already booked my tics for the Hawaiian sacrifice. See ya there. - George Badger

To all, First, let me wish everyone a Merry Christmas and a Happy New Year. The head came off today without any trouble at all. (Knock on wood) The water passages I expected to see jammed with corrosion and stuff were clean. The head, with the valves included, are at the machine shop. The machined surface and the valves are getting checked to see if there are any leaks. The water passages will also get a good high pressure water clean out. Beside lots of baggies filled with lots of nuts and bolts, the head removal was fairly simple. So why am I still worried. I removed the left, rear freeze plug hoping to find something plugged. It looks clean from the outside. The left water jacket opening, next to the #1 cyl., along the top of the block, does not seem to be connected to the freeze plug hole below. In fact, none of the passages from above seem to be connected to the lower water areas where the freeze plugs are located.I hope this is normal.There was standing water in the water jacket openings when the head first came off. After prodding around in the Lt. opening next to the #1 cyl.,, it seemed to drain somewhere, but not out the freeze plug. Then I filled the left rear water jacket hole again and the water eventually started running out the drain under the radiator. I wish I had a cut-a-way of the internal water passages to see what it is I'm poking around in. Next step will be removing the water pump again, and flushing out the system from the top down. Also wish I had a 12" wire bottle brush to scrub out the inside of the block. Hooked up to an electric drill would cause some serious cleaning. If anyone has some suggestions on what else I should be sure to do at this stage of the game, feel free to step in. The head should be ready to put back early next week. - Aloha, Rob XK-140 FHC

Rob, There is an internal webbing on the left side of the block. The water seperates into two streams, one upper and one lower. Poke around the base of the cylinders and loosen up the crud. It will be packed. Also check the gap between each of the cylinders. I can't remember if any of the cylinders are connected (webbed) together. Do lots of scaping! Every motor that I've taken apart has had some mineral build-up around the cylinder bases and on the cylinders themselves. - Cleo Bay Jr., 52 XK120 OTS, 56 XK140 OTS

Rob: Having once cleaned a badly plugged block, I would recommend you get a 12" length of 1/4" woven wire cable, put it into your electric drill and attack the block passages (fwd and reverse) with the loose/frayed end. Find a garden hose attachment that narrows the water stream to 1/8 - 1/4" and follow the drill treatment with the high pressure water flush in every block orifice. Yes, it does get messy. A substantial bendable metal rod or wire probe is also essential for poking deeply (and firmly) into all of the block openings and clearing the passages. You'll soon be able to discern by sound and feel whether or not any debris is still lodged there. It becomes obvious when you're poking against the rough block casting or something that doesn't belong there. I was dumbfounded that water could flow so freely from the block drain and yet find the block filled with almost 2 quarts of rust and corrosive debris. Don't be hesitant to remove all the accessible block freeze plugs while you're at it. Were there any signs that the head gasket had been leaking? When you reassemble the whole thing, make certain that the new head gasket allows all the head water passages to connect to those in the block. Here's hoping your volcano is about to become extinct. Merry Christmas - Dick Cavicke

The early motors with the open bellhousings are timed with the flywheel, at aproximately 3 teeth. I determined that by counting the teeth and dividing the number into 360. Timing has to be done thru the hole in the top of the bell housing with the arrow on the flywheel marking TDC, since there is no timing pointer on the timing chain cover or reference on the aluminum oil pan. - Larry J, 660636

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