1989 XJ 6 (Daimler) has developed a coolant leak. When following instructions for adding Stop Leak noticed that coolant was escaping from the reservoir cap. Is this a common occurrence? Could it be the cause of the leak or could it be a manifestation of some greater problem with the cooling system. My technical skills are very limited and I would probably not be able to do some of the testing I've seen mentioned on many relevant threads.


Any advice would be greatly appreciated.


3jags

 

I've moved your question from General Tech Help to XJ40 forum. Members here with the same model will be able to help.

Graham

 

It may be as simple as a worn cap or bottle. If all else looks ok ie its not overheating I would try a new cap and you may have to step up to a bottle.

 

Could be a worn out cap or bottle or a blown head gasket leaking exhaust gas into the coolant and so on and so forth. Has the temp gauge risen any?

 

Thanks GGG, JEH and Roger95.
So far the only time the temperature gauge has risen was in town, on a very hot day, after that it returned to normal. The round trip had taken about three hours. For the moment I have used silicone tape to tighten the cap and, on a short trip, no sign of coolant leakage.

 

Ok...there is an inexpensive tesing kit available for finding exhaust gas in the coolant (leaking head gasket). I would advise testing cooland for exhaust gas, just to be sure.
These kits are available at most auto parts supply stores.

 

Thanks again Roger95, I'll certainly try to find the test kit you recommend. I'm located in France so it might take a while to find one -- maybe get it from the UK. In the meantime, I've installed the cap from another (old) XJ6 I have but, so far haven't been able to drive the car enough to establish whether the cap was the problem -- the silicone tape helped some but there was still a discharge from the expansion tank.


I'm keeping my fingers crossed that all that's needed is a new cap but, without much conviction!!


I'll let you know how I get on.


Regards,
3jags

 

Hi 3jags,

A common problem on the XJ40 is that the rubber gasket in the coolant reservoir cap compresses and hardens over time and loses its ability to seal.

Regarding the use of Stop Leak in your cooling system, there is a risk that the particles that are designed to seal leaks can completely clog your heater core and other small passages in the cooling system, so it would be best to physically correct the leak and avoid the use of Stop Leak altogether. Hopefully a new reservoir cap will solve the problem.

Cheers,

Don

 

Don, thanks for the insights. Took the car out today and drove for about 60 miles. Checked cap for signs of leaking but there weren't any. Haven't yet checked the coolant level, will do so tomorrow. Temperature gauge did move up a little when going uphill behind a truck but it quickly came down again. Even if the new cap appears to solve the immediate problem, I will take your advice and have the whole system checked out/cleaned.


Regards, 3jags

 

Checked coolant level today, seems fine. Will continue to monitor. Now I have a problem finding tires at a reasonable price!

 

Please don't use Stop Leak! GM required Stop Leak in the Northstar V-8 because of the porosity (was hoped the Stop Leak would fill the voids) in the block castings. The Northstar was an excellent world class design poorly executed because of block porosity and other issues. Typical GM cost cutting. I had a '97 Eldorado that I positively loved until the engine came apart at 91,449 miles. Never had that happen with any Jaguar I have owned.

 

For many years Jaguar specified that two bottles of Bar's Leaks (or Barrs Leaks) be added at every coolant flush. In the early '90s Jaguar even recommended using Bar's Leaks to reduce coolant seepage from the head gasket, even after a new head gasket had been installed!

But subsequently Jaguar ceased recommending the use of Bar's Leaks, and to my knowledge they no longer recommend using any kind of leak stopper in any of its cars.

Cheers,

Don

 

YES - you won't find mention of this product in any recent Jaguar literature.

Opinion is divided over Bars Leaks. There's those who swear by it and those who swear at it. Most of us who have ever rebuilt early Jaguar engines fall into the second category.

It would rarely stop a leak but was most efficient at blocking small waterways.

Graham

 

Thanks Roger, John and GGG. As soon as possible I'll get the car serviced and have the radiator etc. flushed to get rid of the "nasties".


Regards,


3jags