I didn't want to do a new thread but if I hide my question in someone else thread it goes unanswered....
My 1988 XJS coupe has been driving me crazy. It gets hot and spews out coolant. Lately it has been running about 1/2 way between N and H, but it is still shooting coolant out along with steam. Most of it is coming out of the overflow tank cap.
My mechanic replaced thermostats, etc. and it will idle for long periods without shooting stuff out. Drive though and woosh.
I noticed that the radiator caps had been replaced with 16#ers. I am wondering if I ought to find a 20# for the main cap and a new 16#cap for the overflow tank.
I have tried water wetter and all sorts of stuff. I need to get this fixed so I can do my emissions test for a title.
Please, ideas?

 

"My mechanic replaced thermostats, etc." is a bit vague. What else has been done? New radiator? Radiator professionally cleaned? New fan clutch? Cooling system properly bled? Aux fan working as deisgned?

My experience is that everything in the cooling system must be at 100% correct operating efficiency on these cars. There is no margin for error, so to speak.

Sixteen pound caps are fine, by the way.

Give us a bit more detail and we'll go from there :-)

Cheers
DD

 

Nice to see you back, and giving this guy the best possible advice.

 

We replaced the thermostats, replaced one of the fans and put in a fan shroud that was missing, replaced the fan clutch, bled and refilled the system. My mechanic has 6 XJS's and really knows them well. He said he had to do one of his car's radiator, but, we have been avoiding doing the radiator because of the labor of getting it out. I am afraid that will have to be done as I can't think of anything else to do.
The car sat for over a year.