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Thermostats
Thermostats

To all, The results of the recent rack and pinion "rebuild" will have to wait. There is another problem brewing in the cooling system. I discovered the overflow pipe in the neck of the radiator was completely jammed full of rust. Whenever the system got hot enough to blow off some steam, it would create a new leak and squirt water all over the place. It took me a while to figure out why I was the only one with the wipers going. I now have a fully functioning radiator with a new overflow pipe.

The first time out, it got so hot, I lost most of the water out the new overflow tube. The cap is a new one from Bassetts, a 4 lb. one I believe. It was a warm day (mid 80's) but at a steady 60mph on the freeway, it shouldn't have gotten that hot. The advice I got was to remove the thermostat and run without one. I did and on the way home, the temp. never topped 90.

My question is, what are the possible drawbacks of not using a thermostat? Even though I have a 140, the engine is from a 1959 MK1, not that that makes any difference. I have not tested the one I removed to see if it was working properly.

Also, what is the best ratio of water and antifreeze to use? Any other comments are welcome. Do the water pumps ever wear out and need replacing? One more thing. The heater core has been removed. It leaked. Now, the water hose just loops back into the manifold. Not much use for a heater in my neck of the woods. Thanks in advance for the help. - Rob XK-140 FHC

Aloha, Rob. Did you give the engine block a good thorough flushing with the garden hose while you had the radiator out? I would say remove the block drain petcock and all hoses when you do this. What about that heater hose, is it routed in and out of the correct manifold ports? (irrelevant question if you have only two ports of course). Is it common in Hawaii to run without antifreeze? Here in Illinois we use a 50% solution, it helps keep down the rust buildup. Prestone and Peak are common brands here, both claim to be fine with aluminum and I haven't had any problem with all the various aluminum head cars I've owned. Change it every couple of years. Also a very unusual but nevertheless possible failure mode is broken vanes in the water pump impellor (happened to me on an E-type). - Rob Reilly

The engine does not get sufficiently hot to burn off lots of nasty things, including water.....I've been advised from very early on NOT to run a car without a thermostat......The engine should be fitted with a thermostat that will bring it to its normal operating temperature, whatever that is.....probably somewhere in the 180-195 degree range? I know this sounds like the standard answer, and it may not be what you wanted to hear, but the reasons sound like good ones.

>Also, what is the best ratio of water and antifreeze to use?

50/50

Any other comments are welcome.

Wish I cound get rid of my heater core....<g> - Bob Mullins

May I add..... a popular opinion is that an automotive cooling system run without a thermostat in place can eventually suffer from localised overheating and possibly gasket failure and other disasters in areas which become hotter than they should do because the designed water circulation flow pattern can be compromised by the lack of flow resistance from the missing thermostat which influences the complete and even distribution of the coolant around the engine cooling passages by the pump.

Anti-freeze is not generally as good a conductor of heat as water so the greater the ratio of antifreeze you use over 50/50, the less benefit it has, anti-freeze is there to provide more than a cooling effect. - John Morgan

To all In the debate on the pros and cons of thermostats have we downplayed the probability of waterpump performance problems. I know nothing about Jag-pumps, but having used and rebuilt centrifugal pumps used for mining applications (corrosive and replete with impeller breaking debris), I know that it does not take too much to reduce the pump efficiency. Might age, crud, rust and maybe a dated design eventually cause insufficient throughput........and if yes, how can this be tested and put to bed. - Klaus Nielsen

Regarding anti freeze, I inquired of Bruce Carnachan, a jag expert about where to go to have the corrosion damage to the aluminum jag head repaired (termite damage?) and I have copied his reply for your edification. The bottom line is that ethelyne glycol and jaguar aluminum do not go together. Others have suggested proplyene glycol instead. Me, when I get done with the restoration, I will use mineral oil and distilled water! ++++++++++++++++++++++++++++++++++++++++++++++++++ Dear Frank,

That cylinder head corrosion you have is fairly common on the XK engines. The usual fix is to take the head to a competent machine shop that can do aluminum welding, heli-arc welding I believe they call it. Then have the head flat surfaced, and you might have the valve guides checked for wear, as most automotive machine shops can replace them. If some of the Jaguar Club members do not know of a good machine shop in your area, you might call Terry Larson in Mesa, at 602-984-8501, and find where he sends out his cylinder heads. If you are doing your own valve job, watch out that the other cam shaft is not bolted down while you turn the one you are setting the clearances on, other wise the valves will bump and bend one. I usually bolt on two short pieces of wood to the rear manifold studs to keep the back of the head off the bench while setting valve clearances. The front downward studs keep that end off the bench. I prefer to do my own valve job as I

take my time and do it right and get accurate clearance settings (seems to take about 3 times per side, as they do change on you, even though you have miked everything). XK'S Unlimited could do the work for you, but they tend to be a bit expensive and you should find a place quite near you that can do the work. I met a new member last year that uses a water purifier on his cars, has an XK 120 FHC with over 400,000 miles on it, and he says no corrosion or rust in his 120.

I have used water-soluble oil (vegetable or machinist oil) in my XK 120 for years, I drained the block and radiator last week after running at 95 F on a 96 F day with strong desert winds blowing across the car instead of into radiator. No rust came out at all, but I think my radiator might need cleaning out as it has been about 12 years. If the car is parked for a long period of time with anti-freeze still in the block with an aluminum head, massive corrosion will occur. I was advised 30 years ago by a radiator repair shop, not to use anti-freeze in my XK 120 due to corrosion, try the machinist oil instead, about two ounces in a full system. There is not much problem with anti-freeze and aluminum engine parts IF the car is driven regularly, and the coolant is changed each 1- to 2 years. Let me know if you can not find a suitable shop to weld up the head, we have several right close by.

Bruce Carnachan ++++++++++++++++++++++++++++++++++++++++++++++++++++++ - Frank Billeter

When I baught my car (XK120 dhc) someone had already taken out the thermostat. The result is now, that always when driving fast, even when it is very hot (hmm, in Switzerland), the car never reaches 50 degrees. My mechanic told me that this is no good for the engine and that a properly working thermostat should not interfere with the maximum cooling capacity, but only with too much cooling. So he is going to put the thermostat in again. - Zoran Mitrovic

So I drain the ethylene glycol and flush my system. Than I go buy a gallon of machinist oil and add it along with distilled water to refill the system. Do I get freeze protection with the machinist oil? Also, does the oil gum up anything that will cause future problem. I have drained my XK120 and am now ready for ther next step as soon as I get an ok from this forum. - Steve McDonald

Make sure your oil is water-soluble cutting oil, not machine ways oil. Nothing will gum up and freeze protection is assured by not going out in the cold! - John Morgan

For what it's worth, my experience (good) has been that a 50:50 mixture of DISTILLED water and aluminum-compatible ethylene glycol antifreeze gives good cooling, good freeze protection, and does not corrode the aluminum engine items. The key point is the distilled water - depending on local water supply, the tap water may contain substantial concentrations of ionic species which are responsible for the aluminum corrosion.

In the winter, I usually drain 1 to 2 litres (quarts) or so and add ethylene glycol (60% glycol max) to give better freeze protection as our winters generally hit -40 degrees (C or F) for at least several days. In the spring I drain a similar amount and replace with distilled water.

It helps to check the specific gravity (proportional to the freeze point) of the antifreeze with a battery acid/antifreeze hygrometer to ensure that adequate freeze protection is present. - Dave Quirt

Dave, That is good advice. I would also recommend changing the coolant every 3 years. - George Badger

>Do I get freeze protection with the machinist oil? Make sure your garage or storage space is heated! George Badger

What I did when we lived in Oklahoma was to remove the 'guts' to an old thermostat and leave just the housing in place, the purpose as to leave some restriction to the water flow, thereby slowing down the flow so the water could absorb the heat more efficiently whilst avoiding the bigger restriction and the possibility of the thermostat not opening up enough.

There are different specs for thermostats, most common is 180F (summer) and 195 F (winter...supposedly makes the heater work better, but since I left the top down on my roadster for 20 years, I never could tell if the heater was working or not!!) But, it seems to me that the different temps are all academic anyway since even with the hot one, by the time the water gets to 195 the thing should be wide open anyway.

The net is, I left the empty thermostat housing in place and it was fine except in heavy traffic on a 100 F day....Some friends of mine put electric fans in front of the rad in their Jags and said that cured overheating completely. David M. Drenzek

To all radiator replies, The trouble with a great forum like this is that there are so many good opinions and useful advice. I still don't know whether I should run my 140 without a thermostat in this warm Hawaiian climate. Remember, a cold soaked engine in my neighborhood is 75 degrees F. I do know that without it, the water temperature is noticably cooler (infrequently over 90) but know I'm worried about "hot spots" that can cause gasket damage and other terrible problems. I have lost so much water through the holes in the radiator lately, that the cooling system is very flushed. The last repair visit discovered that the overflow pipe at the top was plugged and extra pressure was trapped. The system was literally blowing holes where the core is attached to the manifold along the top.

Is there a thermostat calibrated for hot weather? The instrument lights are back working. Loose connection was with the driver, not the wiring. Still have to clean the contacts in the regulator for the amp indications. Another question, where are the numbers for the chassis and gear box printed. I need to confirm the information from the Heritage people. All I have so far is from the plate in the engine compartment. What is the going price for a '55 XK-140 FHC driver? May have to face reality here pretty soon and let the toy go. Thanks for the help. - Rob XK-140 FHC


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