Gents, I am trying to pressurize my 2003 XJ8 cooling system chasing a mysterious slow leak. I have tried everything I can think of and bought every kind of new adaptor and pressurizer I know of to pressurize this cooling system. Nothing has worked so far. It seems this system has a two part sealing cap unlike all other systems I have encountered. When I queried elsewhere, I was advised to get a Mityvac MV4560 system as it did it all. News Flash, AFAIK, it does not do my X308 there being no two way sealing adaptor in the kit.

I even tried cobbling one up with an old pressure cap I had. No Joy.

SOOOOOooooooo, if any kind soul out there knows EXACTLY how to do a pressure test on the cooling system of the X308, please tell me in excruciating detail how it is done, preferably with pictures. Please also provide exact names and product numbers of any items used.

I have spent three frustrating days trying to pressurize the system chasing a mystery leak that leads to overheating. This is becoming ludicrous in the extreme.

Best regards to all, Brian

 

Some parts stores have testers with the proper adapters in their loaner collection, but I'm not sure which ones. I bought the Harbor Freight kit, and the green adapter works for both Jags and BMW.

 

Hmmm.
2003 = aged plastic parts.


I had EXACTLY the same problem.


Found out it was a brittle thermostat cap. It would "****" out a VERY light stream. Almost invisible to the naked eye, but I happened to notice it when I was searching for it. It was a sunny day and at just the right angle you could see it. When I found this "leak", it was doubtful it would even show up with a pressure tester because it was on the opposite side of the thermostat. If the stat is not open, no pressure will be evident.


This is only an example, but there are quite a few plastic parts associated with the cooling system in these cars.


I would start checking all the plastic in the system.
Especially those stupid, brittle bypass "hoses/tubes" that ALWAYS seem to break at the connectors.


I don't think you need a pressure tested, just bring the car up to temp and let the system pressurize itself. Then check all those stupid plastic tubes and parts that they use with corrosive coolant!

 

When you use a pressure tester the whole system is pressurized. The advantage of using it is you can pump to 15psi cold and leave it there. Some leaks are so small that the coolant evaporates and the leak is not detected, especially at the back, with a hot engine.

If the system holds pressure for several hours there are no leaks. It took me that long to find a leak at the Norma fitting above the exhaust system at the right rear.

 

The correct fitting will close off the overflow ... my memory is the green one from HF works. The universal type that work like an expanding cork will also do the job.

when you say "mystery" -- do you see coolant?

The Jag V8 does not like running hot.

 

you could try fluorescein and UV lamp. Won't show head gasket or block cracks though

 

I 'rented' one from Autozone a few months ago for my XJR and the kit had an adapter that fit. I am local if you need help with it, send me a PM.

 

Hi susu,

I'm not positive this is true on the X308, but on many vehicles I've pressure-tested it is difficult or impossible to build pressure if the coolant level in the reservoir/expansion tank is low, so it would be worth checking yours.

I'll check my pressure-testing kit and confirm which adapter fits the X308 and post it in a little while.

Cheers,

Don