Edited on 2010-07-27 16:27:32

I am the owner of a 1988 XJS Jaguar. I recently read an exchange on Jag-Lovers.com with two individuals. The exchange went like this:

individual #1: "I started losing coolant everyday along with the coolant oozing out of the coolant expansion tank after warm-up. I could not figure out why I was losing coolant and why it oozed out of the expansion tank even after I replaced the cap with a new cap and tightened it well. . ."

individual #2: "Sounds like there has been a bonding failure on your timing chain guide. I don't think you can over-tension the chains as they have sprung-loaded tensioners (except for the oil pump drive which has a mechanical adjuster)."

I am experiencing a similar coolant leak problem. I also am not getting any heat out of my heater. I don't know if the problems are related. I don't understand how a bonding failure on the timing chain guide can cause a coolant leak. I have not done any work to the timing chain recently but I recently cleared the valley, changed the plugs and overhauled the distributor.

Any insight you could provide would be appreciated, Thanks!

John Salla
jsalla007atgmail.com

Submitted by jsalla007@gmail.com on Thu, 07/29/2010 - 11:40

Thanks to all. William could you please provide me with the proper method of filling the tanks step by step. I am a little confused. Thanks much. John jsalla007atgmail.com

Submitted by bonnettoboot@e… on Wed, 07/28/2010 - 23:43

This has always been a confusing issue on the 12 Cyl XJ's (and many of todays cars) and David "sort of" found the answer. The fill procedure was to; fill the expansion tank up to the set level, (we used a marked wooden dipstick) but the important thing is that the cold fluid level in the tank has to be an inch or two higher than the feed tube which comes in from the radiator. At this point the expansion tank cap is fitted. The fill procedure is now done through the radiator cap. this should be filled to the very top at which time the radiator bleed screw should be opened allowing any trapped air to escape, then closed. The coolant in the expansion tank cannot rise as there is air trapped above it. This air is what is pressurised when the coolant temperature rises, expanding the coolant. As the system cools down the pressurised air then pushes the coolant back into the radiator. If the expansion tank is overfilled, the excess coolant will be forced out of the cap, not only will it expell the extra coolant but once the cap is opened it will stay open and continue to exude coolant until the pressure drops, this results in the system being low on coolant and appearing to be overheating. Check the Manual for cap pressures for your year but I seem to recall the rad cap was around 17 psi and the expansion tank 22psi!

Submitted by halldjt@earthl… on Wed, 07/28/2010 - 13:06

My 95 V 12 did the same thing. I discovered I was just putting to much coolant in the expansion tank. I read in the forums that when you take the cap off of the expansion tank it lets air in the system. After bleeding my radiator again and refilling from radiator side I have no more coolant leaking from overflo and car does not heat up. I checked my radiator level several times after that but only needed about 4 oz. of coolant so I do not even check it now but occasionly as this is the norm for the 95.I dont know if this is the same as your 1988 but that was the problem with my 95 V12. You still need to verify this with your Jag as they are notorious for heating up.

Submitted by silver007@shaw.ca on Tue, 07/27/2010 - 20:21

the remote tank seems to fill up and not get drawn back to the header tank, see how much is in the remote tank, the water in the centre filler neck should be about an inch below the top..perhaps it is just being overfilled.....

Submitted by SE98-32482CJ on Tue, 07/27/2010 - 19:10

John I will read that thread but you are going to have help me find it. As I said I think the chain issue was a post on a different issue. Are you sure your pressure caps are of the correct pressure rating?

Submitted by jsalla007@gmail.com on Tue, 07/27/2010 - 18:16

George,
I did not change thermostats. I am not sure where the coolant is coming from. It appears to be coming from near the overflow, as I once saw it leaking from the driver's side behind the wheel well -(closer to the driver). I took off the driver's front tire and took off the protective sheath that covers the overflow tank. Everthing appeared in order. I thought maybe the hose to the overflow had rotted and the coolant was just freely leaking without making it to the overflow, but this was not the case. The temperature is normal when this happens. Of course, after much coolant leaks the temperature gauge rises. I have yet to overheat. Thanks for your help. Where is the timing chain guide, if you think that is the problem?
John

Submitted by SE98-32482CJ on Tue, 07/27/2010 - 17:00

John I looked for the post and could not find it--I think someone posted on the wrong topic--happens all the time--and the archives there are so full of stuff that they are mostly useless unless you already know the solution--so let's just deal with your issue here--are you saying that you are loosing all your coolant via the overflow? How is the temp. when this happens? Did you change thermostats? If you did, did you make sure the burp hole was up?