Have you tried parking it on an incline of some sort (ramps, hillside, etc.), nose-up, to be sure all excess air is out?

 

May I ask, What makes you think its too much pressure?

I ask because as the temperature rises, so does the pressure. Our radiator caps are designed to bleed off pressure higher than 13 PSI (or is it 16 psi?).

Seeing as the cap is spring loaded, theres no way you could have "too much pressure".

Are you assuming this because the top radiator hose is firm once it gets warmed up?

 

While I don't know that it has excess pressure, you are describing very similar symptoms and conditions to what I experienced last summer when I replaced most of my XJ's cooling system components. I was unable to "get it right" until I parked it on an incline for a final burp that all was well.

btw, you used the phrase "too much pressure" in your post

Edit: My point is, if you still have too much trapped air (> cap rating), it could take awhile for it all to be expelled. Heck, it may be fine. I would say drive it and watch the coolant level.

 

x2 - Clarify "too much pressure" please.

 

Your vintage XJ needs 4 or possibly more complete heat up / cool down cycles to burp itself.

Drive it for a while, letting it completely cool down between trips. It will likely resolve itself BUT you will also need to keep a close eye on your coolant reservoir and with engine cold, add some coolant if necessary to replace the air pockets as they burp themselves out.

I wouldn't change out any parts at this time and there is NO reason to go to a lower temperature thermostat. 195 is just what you want.

 

I misspoke.

 

That's exactly what happened to me.

 

 

Not sure if you still have the XJ, but I had an issue that sounds very similar and came across this thread. My diagnosis was that exhaust gases were entering the coolant system via the head or a gasket at the head in some way. I decided since I had a few bucks and wanted to turn mine into a DD that I'd replace the head. After replacing the head, and gaskets, it no longer seems to pressure up. No bubbles in the coolant overflow tank after driving it, no bubbling sounds after driving it.

To mitigate the issue prior to the head replacement, I bought a rad cap with a valve, the red manual coolant overflow valve, and drove with the valve open (red tab up in the open position) so it couldn't pressure up and break a hose or even leak.

Hope you still have the XJ!