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Michael Neals Technical Advice Main / Library / Technical / Model guide / Buyers guide / Guestbook / Photobook / Links / Archive / Specialists

Michael Neals Technical Advice : File 2


XJS, Rack Bushings, Ease Of Replacement

A few notes on XJS rack removal. I've never had a problem with removing the pinch bolt. Holes in the body and removing the catalyst???!!!! Simply remove the oil filter and rotate the steering linkage so the opening of the pinch joint is facing toward the front of the car. Reach through the opening between the subframe and the body with an eight inch or longer extension. Use a wrench to hold the other end of the pinch bolt. Of course any work on an XJS requires a Zen like level of concentration and relaxation, but it is just that easy. One of the flat rate manuals pays 9.0 hours to replace the rack tower seal so someone in the industry must think this operation is difficult. I have to assume that the early cars have a different rack mounting arrangement judging from some of the posts here. If you are really in a hurry the rack bushings can be replaced in 10 minutes. A couple of tapered punches help quite a lot in this operation.

XJS, Catalytic Convertor, Left Side

The left side convertor on an XJS is another high concentration chore. If you ever want to see how good your mechanic is, check and see if the shield has been left off of the left cat after some major work. A lot of patience is required here. The left side bolts on the rack mounts should only be inserted from the left to right on the top and right to left on the bottom. I've seen the upper bolt inserted backwards when some dolt replaced the rack bushings when the subframe was down during a sandwich plate resealing. I cut it off with a high speed cutting wheel but it was still irritating.

Series 3, XJS, Radio Removal, Security Codes

Series 3 radio removal is fairly simple. Remove the knobs for the A/C controls. A special tool is generally required to remove the fasteners that hold the panel on but you could use a couple of screwdrivers. The rest is self-explanatory. Speaking of radios, the security unit types used in the later S3s can be a real pain if you lose your code. I just happen to have a master code list. I am more than willing to restore a lost code for members here. The radio needs to be removed to get access to the serial number. An 88 1/2 XJ40 should not have a security radio. These units came in the Series 3s and some XJSs, mid 80's to 87.

XJ40, 90 1/2 and On, Radio Security Codes

Radio codes on the 90 1/2 and later XJ40s can be found on a sticker under the hood toward the left rear. Be sure to get this code if yours is missing, it's a paper sticker that wears off quickly.

All Models, Wiring Diagrams

I have almost every wiring diagram for Series 3 and onward. I have quite a few for the earlier cars also. Most of these are published by Jaguar Cars North America (not the club) and are a little more user friendly than the Brits distorted views. Haynes diagrams aren't worth the paper they are printed on!!! The XJ40 diagrams from JCNA list connector locations, input and output values. The S3 diagrams also have nice illustrations that show component location. If you need a diagram just let me know.

XJS, Trans Mount Mounting Description

Here's a quick description. The two bolts on the rear of the trans pan are double ended and secure the front of the mount. Two bolts secure this part of the mount in the vertical plane and are the two lower bolts that hold the tailhousing on. The cast aluminum piece with two holes and a long stud in it bolt to the tailhousing with a 3/8 washer between the cast piece and the tailhousing. The stud faces downward. The spring support mount generally has a foam bushing installed in it, replace it with the rubber version, it will last longer. The spring sits in a rubber cup on the spring support. Do not use another rubber cup on top of the spring, it compresses the spring too much. With the spring support bolted up insert the thick washer type spacer onto the stud. Insert the sleeve and place the piece that is basically two washers welded together with the larger hole upwards. Install the bridge plate that goes between the stud and the front section of the mount. A large nut goes on the stud, no washers. The front two bolts on the bridge have thick spacers, about 1/4". Install the nuts on the bolts that are facing down. Use lockwashers only on these.

Series 3, XJS Heater Cores

Here is a word of warning; be kind to your jag and "short-cut" the heater core job. Unless you replace the heater core yourself and take many long hours to ensure everthing is replaced properly it will never be the same. To tear apart the S3 dash completely to replace the heater core takes a person who does it on a regular basis, like 10 or 20 a year! It is much easier to cut the pipes and use rubber hoses. The original design of the core is typical British anti-engineering. I've done the job both ways many times. The easier way of cutting the pipes to install the core and splicing them back together with rubber hose has proven to be trouble free. I use 5/8 I.D. hydraulic reinforced hose with heavy-duty wide hose clamps. Tighten them once a year is all the maintenance required. Ideally someone should come up with pipes that bolt to the core like the XJ40 but I have yet to find a supplier. If anyone has a problem with rubber cooling hoses in the dash, take a look at a few high end Japanese cars with many feet of heater hoses buried within.

All, Radios, Wiring Diagrams

Security equipped radios have a flashing LED. An '84 may not have the security feature. The factory radio is about average cost to repair. Yes, the security feature is activated when the 12v power supply is disconnected. Hitting the radio when the power is off will also activate the security system. To reset the unit, when you have the code, simply punch the code in. You only get three tries to reset the code! After the three botched attempts it is necessary to let the unit sit for over an hour with power on. Note that the security feature does not allow anything to work on the radio when it is tripped. For future reference, all the radio codes on my list start with a "B".

XJ, Suspension, Axle U-joints, Jag-List Article

U-Joints can be a little difficult to install without getting the roller pins jammed down in the bottom of the bearing caps. Here is a short step by step procedure to make the process a little easier. When installing new ujoints remove caps and apply extra grease. Insert body of U Joint into girdle. Push end of body up through one side of the girdle and install bearing housing cap. Drive bearing housing through girdle making sure to retain body in cap. Push opposite end from cap through the other side of the girdle without pulling the body out of the bearing cap. Install second bearing cap. Install circlip in the empty side of the girdle. Keeping cap in position press assembled ujoint into final position and install the other circlip on the second bearing cap.

General Info, Tool Size Conversions

S O C K E T S & W R E N C H E S ( S P A N N E R S ) Created 00/00/00 Updated Transferred Jag-List 06/06/95 Key to Nut & Bolt Sizes
      nut size across flats                   British sizes
  -----------------------------           --------------------
  decimal inch    mm    AF inch           BA      BSF      BSW

      .250         .      1/4      .       .       .        .
      .276         7       .       .       .       .        .
      .282         .       .       .       3       .        .
      .313         .      5/16     .       .       .        .
      .315         8       .       .       .       .        .
      .324         .       .       .       2       .        .
      .340         .       .       .       .      3/16     1/8
      .344         .     11/32     .       .       .        .
      .354         9       .       .       .       .        .
      .365         .       .       .       1       .        .
      .375         .      3/8      .       .       .        .
      .394        10       .       .       .       .        .
      .412         .       .       .       0       .        .
      .433        11       .       .       .       .        .
      .438         .      7/16     .       .       .        .
      .445         .       .       .       .      1/4      3/16
      .472        12       .       .       .       .        .
      .500         .      1/2      .       .       .        .
      .512        13       .       .       .       .        .
      .525         .       .       .       .      5/16     1/4
      .551        14       .       .       .       .        .
      .563         .      9/16     .       .       .        .
      .591        15       .       .       .       .        .
      .600         .       .       .       .      3/8      5/16
      .625         .      5/8      .       .       .        .
      .630        16       .       .       .       .        .
      .669        17       .       .       .       .        .
      .688         .     11/16     .       .       .        .
      .709        18       .       .       .       .        .
      .710         .       .       .       .      7/16     3/8
      .748        19       .       .       .       .        .
      .750         .      3/4      .       .       .        .
      .787        20       .       .       .       .        .
      .813         .     13/16     .       .       .        .
      .820         .       .       .       .      1/2      7/16
      .866        22       .       .       .       .        .
      .875         .      7/8      .       .       .        .
      .920         .       .       .       .      9/16     1/2
      .938         .     15/16     .       .       .        .
      .945        24       .       .       .       .        .
     1.000         .       1       .       .       .        .
     1.062         .     1 1/16
     1.125         .     1 1/8
     1.250         .     1 1/4
     1.312         .     1 5/16
     1.375         .     1 3/8
     1.500         .     1 1/2
This conversion chart was uploaded to me on Compuserve. I believe that it originated on the British Car Mailing List. I have expanded it slightly.

Series 3 XJ6, Transmission, Trans Theory

Created Transferred Jag-List 06/06/95 This bit on trans theory was sent to me by a true tranmission repair specialist. It was originally a reply to a question on Borg Warner troubles. Dear Mike: This is going to be a long story. Not being there to road test and check the car out, the next best thing is to explain how it is supposed to work and see if you can decide what the problem is. You're there; I'm not. Sit back, read, and check this out: There are 3 basic principles that come into play and their relationship to each other is critical for long-term durability of the transmission. For teaching purposes I will use round, estimated figures; not the actual pressures in a BW. PRINCIPLE ONE: Governor pressure is approximately 1 PSI for each MPH of road speed. 10 PSI governor = 10 MPH. 30 PSI = 30 MPH. 0 PSI means you are standing still. Pretty simple concept, huh? PRINCIPLE TWO: Throttle pressure (or shifting pressure as the Britts may call it) is just like governor pressure, but it is proportional to the amount of throttle the engine is given. No throttle pressure = no throttle. 50% throttle = 50% throttle pressure (say, 50 PSI). 100% throttle = 100% throttle pressure, or 100 PSI. BRIEF INTERMISSION: Now this is where it gets hairy. It is important to understand a balanced valve. It goes by many names, but the principle is the same. Balanced, or regulating valves do just that; regulate a pressure to a pressure that keeps the valve balanced. Just like the oil pump pressure regulator valve set up in an engine. If the oil pump volume is more than needed, excess pressure is exhausted. Conversely, if the oil pump speed, or volume, drops; then the valve that was partially open exhausting oil, now closes off the exhaust to maintain pressure. At any given steady volume, or any given spring tension that "balances" the valve; the valve will always seek a state of equilibrium. Change the spring tension or the amount of oil being supplied to the valve, the balance is upset and the valve will open or close the oil supply, depending on the system's needs. This is why you either put a stronger spring in, or shim the current spring in an engine's oil pump to increase oil presssure sometimes. You are changing the balance. Conversely, if you cut a coil or two off of that same spring, you would run lower oil pressure. If you can feature this principle, the rest is downhill from here. Here's the revelation: The governor and the throttle valve are both balanced valves. The governor has a variable spring called centrifugal force. As output shaft speed increases, so does the "tension" on the force that balances that valve. So pressure rises and falls with output shaft RPM. The throttle valve has a real spring with a fixed tension. The trick here is they make the spring seat move with throttle opening by way of the infamous throttle cable that goes down to the trans. This cable works a cam-like device that mashes in on the throttle valve spring to increase the spring tension. When you let off the throttle, the throttle valve (TV from now on) lets off the spring and the TV pressure drops. I hope I have not been too simplistic so far. A lot of this may be common knowledge to you, but I am trying to make sure you and I are on the same page because the next part is where most techs screw up. If you have access to the oil schematics of any automatic transmission (especially a BW 65 or 66) find the 2-3 shift valve. It has a spring under this valve that takes 25 PSI of governor pressure to depress the 2-3 shift valve down to the 3rd gear position. If this was all that we had to worry about, life would be wonderful and Clinton would not have been elected. But life is not that simple. This brings me to: PRINCIPLE THREE: All of the clutches and bands are hydraulically applied by an oil pressure called mainline, or, control pressure. I prefer to call it mainline. The more torque the engine is producing, the more mainline pressure you need to keep the clutches and bands engaged solidly and not slip under torque. At light throttle, or when your grandmother is driving, you only need minimal mainline pressure to do the same job. If the mainline pressure was to remain high during Grandma's trip to the store, the excessively high mainline pressure would slam each band and clutch on hard enough for her to add a tube of Denture Cream to her shopping list. It didn't take long for the God of transmission engineering to figure out that mainline pressure should somehow be proportional to the amount of torque flowing through the transmission. This is why light throttle shifts are softer than heavy throttle shifts. He decided that us knowing how a balanced valve worked was too easy. He had a brainstorm one day and said "Hey.......let's really confuse the hell out of them and have the pressure off of a balance valve control ANOTHER balanced valve." So with that thought in mind, look at any automatic transmission oil circuit schematics (including B/W) and you will see the yellow (TV) pressure also goes to the spring end of the main pressure regulating valve. When TV pressure goes up, so does mainline. If TV pressure goes down, so does mainline. TV pressure actually "boosts" the tension of the main pressure regulating spring. As is if this is not confusing enough, remember earlier when I said the 2-3 shift valve had a calibrated spring to take 25 PSI of governor pressure to move the valve to the 3rd gear position? Well........TV pressure also is routed to the spring end of both the 1-2 and 2-3 shift valve. What this means is this: With absolutely no TV pressure 1-2 occurs about 10 MPH and the 2-3 shift occurs at 25 MPH. As you give the vehicle more throttle, TV pressure rises to provide TWO (count them, 2) functions. Function 1 is to raise mainline pressure to keep the clutches and bands from slipping and giving an acceptable shift feel. Function 2 is to delay the shifts by this technique: With more throttle, the governor pressure now has to overcome the 25 PSI spring under the 2-3 shift valve AND....AND...AND...whatever amount of TV pressure that is assisting the 2-3 shift valve spring holding the 2-3 shift valve in the second gear position! So if there is 15 PSI of TV, plus the 25 PSI calibrated shift valve spring, keeping the 2-3 shift valve in the 2nd gear position; it would now take 40 PSI (25+15=40) of governor pressure to move the 2-3 shift valve to the 3rd gear position. That means the car would have to be doing 40 MPH, or faster for a 2-3 shift to occur. If you are doing just 38 MPH and wondering "Why the heck hasn't this thing shifted yet?", by letting off the throttle you just dropped TV pressure so that the current governor pressure is high enough to overcome the 2-3 shift valve spring and what little (if any) TV pressure under the 2-3 shift valve. Starting to make sense? Now that you have read my novel, let me get to the meat of the matter. It's important to know why, because then you can know how. The valves (all of them) in this transmission are very prone to "sticking". The most active valves will be the most likely to stick (TV, governor, mainline pressure regulator), although the most common is the governor valve. Symptoms of a sticking governor valve are: Late shifts. Stacked shifts. 2nd or 3rd gear starts from a stand still. In general, erratic shifting that is often transmission temperature related. Here's the real comedy of errors: You come to a stop and Governor pressure is zero, like it's supposed to be. You take off and the governor pressure curve goes flat at some point because the valve just hung-no upshift-you back off the throttle and it upshifts. You back off the TV cable adjustment to get an earlier shift and it is of little, if any, help. You back it off all the way to get the earliest possible shifts and it barely acceptable. You (or the tranny shop) ships the vehicle out. BIG MISTAKE. REALLY BIG. In an effort to get shifts on time, you just dropped mainline and mainline boost oil pressure down to where there is not enough mainline to hold the clutches and bands engaged at higher throttle openings. The unit slips and it eventually comes back burned up from the low mainline pressure. Everybody is pissed. The customer, transmission guy, and you. Finger pointing and reputation bashing in it's finest hour. I could go on for pages and pages on this scenario and about half a dozen other ones that commonly happen to the BW in Jags. Have you had any of them lose reverse yet? That's another novel in of itself. By now you are probably saying "Well, Larry, that's all neat; thanks for explaining how transmission oil circuitry works and why they shift late, but how the heck do I fix it?" Hey, Mike; governors wear out like many other parts on a car. Buy cheap insurance and put a BRAND NEW governor on every rebuild. Sell it to the customer. I have even sold brand new valve bodies. If they don't buy it up front, you'll get hung with either buying it for them under warranty, or having one hot customer. Burned up clutches and bands in a BW is the resultant of a hydraulic malfunction condition. Usually low mainline pressure, or wrong-gear starts. A rebuild only puts the transmission in the same condition it was in before it failed. Not correcting the hydraulic problem is the same as putting new pads and shoes on a vehicle that has leaked all of the brake fluid out, or putting air in a tire with a nail in it. Drive the car around and you decide. Hint: The TV cable is set right when full throttle coincides with the TV cable pulled all the way out and you can get a 2-1 downshift when you floorboard the throttle after a minimum throttle 1-2 upshift. Let me know if I can be of any more help. Larry Bloodworth

Series 3 XJ6, EFI, Air Flow Meter Adjustment, Internal

Created 07/16/94 Updated 00/00/00 Transferred 08/20/94 Jag-List 06/06/95 If a car is running rich at idle it is possible to trick the ECU into thinking that the car is getting less air flow through the AFM. Adjust the internal black cog wheel in 1/8 turn increments clockwise. This forces the vane closed slightly which causes the ECU to think there is less air coming in and the ECU leans out the engine and the system goes into closed loop. This is from Tom Graham's experiences on a 84 S3 that was running with moderately high CO and HC at idle and would not go into closed loop.

Series 3 XJ6, Radio, Antenna Delay Relay Wiring

Created 09/28/94 Updated 06/06/95 Jag-List 06/06/95 The antenna delay relay is located in the trunk. Remove the spare. It is on the left side under the rear horizontal panel. Relay is wired as follows: Terminal Wire Color 1 P 2 B 3 WK 4 UW 5 UR Note that terminals 4 and 5 have the same wire color on the Nippon aftermarket Jaguar specific antenna

XJ40 Hydraulics, System Test

Created 00/00/00 Updated Transferred 09/25/94 Jag List 06/12/95

Initial test

Required equipment:
Stopwatch, tape measure, and strong right leg!

Check Ride Leveling Struts

Measure height at rear fenderwell Run car above idle, check and measure rise Run at idle, check and measure rise, 5/8" is factory recommended maximum. Use 1/2" as a safety standard. Gas bladder in strut is ruptured if rise is excessive. Strut pair needs to be replaced or converted.

Check Accumulator

Run car at 2000+ RPM for 30 seconds. Shut motor off and turn key on to activate VCM. Pump pedal slowly, 3 count intervals, check the number of times before the low brake pressure warning light comes on. A fully charged accumulator will go 9 pumps. 4 pumps necessitates system check out, probable ccumulator bladder failure.

Check Charge Solenoid

Continue pumping down system after previous test until pedal is rock hard. Start car and stopwatch, run at idle, observe VCM. Stop timer when low brake pressure indicator goes out. A red border can be seen if a different warning is reading on the inner screen. The red border is a background indicator of this warning. Test several times. 9 to 15 seconds is a good reading. Any longer and pump pressure could be low or charge (load) solenoid may not be seating. Common probable fault is the charge solenoid.

Pump, Charge Solenoid, Accumulator Combo Test

Run car at 2000+ RPM for 30 seconds. Return to idle. Pump brake pedal firmly and swiftly until low brake pressure light comes on. Stop at 30 pumps. Roughly 10 pumps usually signals a faulty charge solenoid (not seating). It is less likely but possible for low pump pressure or a completely discharged accumulator to fail this test. See pump test.

Hydraulic Pump Test

Disconnect line to valve block. Check pressure. Most failed pumps can be stopped off with thumb pressure. Check flow of ??? per minute???

Check Valve Test

To check discharge of hydraulic ride leveling system, charge system and measure ride height at fender lip. Recheck height after 12 hours. More than 1/8"??? sag is a sign of a faulty check valve located behind the up solenoid.


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