Jaguar XJ6 SE

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Description: Onto the third complete transmission failure! It would seem this car refuses to accept a working automatic transmission for more than a year or two at a time. Amidst the work on tuning the

Onto the third complete transmission failure! It would seem this car refuses to accept a working automatic transmission for more than a year or two at a time.

Amidst the work on tuning the engine, cleaning up the interior, and generally improving the car over the last year I thought she was doing pretty well. I did notice since the installation of the third transmission that upshifts were late and harsh (as they were with this transmission in its donor car), but left it alone in the interest of getting other things done. I lived with this shifting behavior for around three years but eventually decided to try and do something about it. Normally on a Borg Warner 66 transmission the shift quality is governed by a combination of throttle and governor control, those being the throttle cable position and vehicle speed respectively. To set this transmission up, the throttle cable is adjusted to calibrate the modulated line pressure somewhere between 50PSI to 75PSI in drive at idle giving an increase to 100PSI to 110PSI if the engine is brought up by 500RPM, brakes applied. I found that when checking the pressure it was already over 100PSI at idle and so attempted adjustment. The crimp stop (a piece stuck on the cable as a reference when the transmission was first assembled and adjusted) would not allow me to move the pressure down far enough so I removed it and commenced with adjustments. Having set the pressure correctly I took it for a test drive; perfect shift points along with slipping! Okay, forget it, set the pressure back up and live with it until we can do something more involved!

Move along a few months; the transmission changed its mind and started shifting better so I tried the adjustment over again. Interestingly the slipping issue was gone and I was able to get the shift points and quality to be perfect. I enjoyed an increase in fuel economy and a much improved driving experience. I did a transmission flush, checked the band adjustments, and carried on enjoying the way the car drove.

Move along a few weeks; the darn thing started to slip in all forward gears quite horribly and bind in reverse. I eventually couldn't get it to crest a light hill and so limped it to the garage to remove the transmission for the third time. Upon sending it to a transmission shop (I don't want to rebuild this thing myself again if I can help it), I was notified that the cone spring in the front clutch pack broke apart and was jamming the clutch.

$1500 later the transmission is rebuilt and in a Saturday afternoon I have it installed and adjusted only to find the 1-2 upshift is horrible! It kind of smooshes itself into second followed then by a proper, crisp shift into third. I'm hoping it's just an intermediate band adjustment but given my luck, probably not. Off to the transmission shop I go on Monday to find out if they balked it up.

I have to say "shame on me" for this one. It appears that my last post was four years ago this month!

A lot has happened in my life and also with the Jaguar projects. I've become employed full time as a mechanic's apprentice, acquired more cars, and produced a lot less Jaguar-related output than usual.

Recently however, I've made excellent progress in the slow restoration of the Silver 1983 XJ6 seen in my about section. All new brakes all around have been installed. There are new wheel bearings in front, new tires for summer and winter, and new lower ball joints. The trip computer was rebuilt by yours truly, and the engine is in a much-improved state of tune.

After all of the above there was a complete transmission failure. The front clutch pack conical spring cracked and caused shuddering in reverse, slipping in drive, and ultimately an almost complete loss of forward drive. The transmission is being rebuilt during the writing of this post and hopefully will be installed within a few days. I'll post about the rebuilt transmission once it's installed.

In other news, the blue 1985 XJ6 seen in the about section has been slated for disassembly as there is advanced rust showing up in the haunches and around the front and wear windows. It would be possible to fix this body but I have a much better body on which to build the final V12 VDP which I've been wanting as a project for so long. The originally purchased donor car is a 1985 V12 VDP which is complete and running but needs paint and interior work along with two cylinder liners of its B bank replaced. I was going to scrap this car until I found the rust in the blue one and so now I plan to re-spray and repair the donor car and register it as a daily driver. I'll be sure to update on that progress as it goes!

In my last edition I spoke of a V12 engine transplant for my XJ6 from a donor V12 VDP. Unfortunately said project was on hold all winter long but spring is upon us and the time has come to commence with my work!

I've bypassed the fuel system in the original V12 donor car and run the engine from a clean tank and pump right off the side of the engine bay. This doesn't allow for any driving but does ensure that any fuel-related issues are eliminated for testing purposes. Essentially a pump and filter are connected in series and attached to the fuel rail. The intake of the pump takes fuel from a fuel container and the return line from the pressure regulator feeds back to said tank in a circulating loop. Running in this fashion eliminated a number of troubles I was having with blocked up change-over valves, dirty tanks, broken lines, etc.

Now with the engine burning clean fuel I've been able to establish perfect operation of all but two cylinders which have extremely low compression. A dry compression test revealed about 90PSI on the affected cylinders while the others were around 210PSI. A wet compression test brought the offending pair to the proper level and thus the piston rings and/or liner must be damaged. The piston rings could also be stuck but none of the usual treatments (solvent soaks, steam cleaning, running, etc) have made much difference aside from simply making the engine run cleaner overall.

I'll be soon to post some pictures of my example test setup so others can see what I'm doing. Within a couple of weeks the engine is due to come out of the car and get opened up. I plan on replacing the piston rings for all twelve cylinders and performing a light bore honing.  With new bearings and a general cleanup the engine will be as good as new!

Well it's been a while! It seems I've been spending lots of time on the Jags and not on my blog writing updates on my progress.

In the time since the last post I've experienced a blown head-gasket, taken the '85 off the road, removed the head, disassembled the head, and obtained a complete 1985 V12 VDP (Vanden Plas) with working drive-train for parts.

On removal of the head from the XK motor in the '85 I found what I suspected in the past to be true: the No.2 exhaust valve is burned and beginning to crack. Luckily it didn't fall apart and do damage to anything else in the engine.  Looking at the cost of reconstituting this cylinder head I started to look for cheap parts cars around here that I can use in the process. I found myself a nice V12 VDP for very cheap and got it towed to my place. I can't get the title for the car so I've decided to use the V12 in place of my XK motor which is an inline six. All of the parts from one car fit the other so this should be a reasonably straightforward process although lengthy.

The XK engine, once put back together, will probably end up in my Volvo 245DL and make it into quite a smooth and powerful Volvo! Not to mention, the engine bay won't look like a cavern.

The V12 engine had sat for a long time, maybe six or seven years, and so needs some definite cleaning and tuning. I've found the compression to be pretty good all around except on cylinders 3A and 4A. Chances are I'm not lucky enough for the piston rings to simply be stuck. Most likely the rings are worn or damaged somehow and I'll have to remove the A-bank head and open the bottom of the engine so I can pull those pistons out and change the rings. Luckily it isn't too expensive a job and I can probably do it within a day's work.

I was amazed when I obtained the V12 car how badly the previous owner had configured the engine. He wanted to change the spark plugs and so removed the intake manifolds, fuel injection system, throttle bell-crank, distributor, vacuum lines, and A/C compressor! Really all that's necessary is to move the A/C compressor over, remove the throttle bell-crank, and move some wiring aside. The re-assembly was performed horribly; there were nuts and bolts missing on important things like injector clamps, intake manifold runners, etc. The 6A injector was missing its O-ring between it and the manifold allowing air to pass right by! The vacuum lines were mostly disconnected or connected all wrong. There were electrical connectors going to all the wrong places. There's no chance it would ever have run in that state yet they were trying anyhow.

Within three hours' time I had figured out what was necessary to make it run and put it together. I found all the missing hardware and installed it to prevent any leaks. Even after having sat for so many years it all fired up with some coaxing but it really sounded horrible. A few days later and now it runs really well. No smoke, no steam, just clean burning and perfectly smooth idle!

I took the old car for a spin up and down my road and I've found that the transmission refuses to up-shift until the red-line so I'm going to assume the modulator is stuck. On the GM THM400 transmission used in these cars, the shift-points are controlled by sensing engine vacuum against vehicle speed instead of sensing engine throttle position against vehicle speed. If the modulator is disconnected or stuck the transmission will be reading "full-throttle" continuously and shift as mine does. Hopefully I can fix or replace the modulator and return it to normal operation.

I'm really glad to be moving into V12 land and will try and update my progress with this one as it's really a cool project!

This entry looks at my work with other XJ6s than my own. Since I love working with Jaguars I end up repairing/maintaining these cars for my friends and customers.

The XJ6 in question today is a 1986 Vanden Plas; essentially the same car as mine but with uprated interior and trim. The owner has so far spent a great deal of money on this car in acquiring it and keeping it on the road; I would say the main expense was from mechanics not familiar with these cars. The car was in use as a daily-driver and is really in excellent condition externally. The interior has water damage in the center console and a fallen headliner, most likely due to a moon-roof leak or similar problem.

The owner of this car parked it one day because the charging system had stopped working. The car would run only on a freshly charged battery which would only discharge as the car was used. Since he thought a new alternator and the labor to install it would be prohibitively expensive the owner parked the car for whatever reason instead of repairing the fault. It sat this way for two years until he met me and found out I was able to work on his car.

After a cursory glance under the bonnet I revealed to him that his alternator belt simply had broken and gone missing. $13 later and the charging system was operating perfectly. This is all fine and well except the car has numerous new problems which are a result of sitting around for two years unused. The engine would not start, the interior is getting rather stuffy and the leather stiff. The brakes need a good baking and the car is extremely dirty from junk off the trees coating it in the rain.

I found one of the fuel tank change-over valves was stuck, the fuel pump stuck as well. Luckily these can be woken up with a few sharp blows using a large drift. After solving the fuel problem I've found that the climate control system refuses to function, the coolant thermostat is stuck open, the breather cap and airflow meter pipe are cracked and leaking, and most of the window switches don't work! The cracked pipes have probably been that way for over five years but the others are due to the car not being used.

I'm so happy this person has decided to bring his favorite car back to life and use it again instead of leaving it to rot! If he'd had someone at least glance in the engine bay he would have been so far ahead of where he's at now! I essentially write this post to remind people not to think the worst and give up on their cars, or any other thing for that matter, as the problem is often simpler than you expect and just needs some careful diagnosis.

I'll follow up with before/after pictures of the car when I clean the muck off and give it a good detailing. Maybe even a video of her driving along would be in order!

I let my account run out and had no convenient way to fund it; hence the XJ6 blog being down, along with my other website: W1ngs' Electronics .

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