** Solved *** after seeing on many forums how much replacing a radiator cap could help I decided to give it a try, most people suggest at least an 18lb cap, but NAPA's computers said 13 LBS I INSISTED on a higher rated cap and ended up getting a 16lb, sat in idle with the a.c. on and no overheating, stayed at 160ish, went up in the hills after throwing it in 4 wheel, a.c. still on blast and it only got up to 211/212 at the most. No more bubbling reservoir!


Just bought a 95 XJ 4.0, Took it up a mountain and it overheated (to the mark above 210, so I shut it down let it cool and drove it home. I tried burping the cooling system. Stays fine (below 210) at idle with cap off, heater on, running for 30 minutes. Put cap back on, ran for about 10-15 mins with the A/C on (idle) and temps got the the mark above 210 (Which is how hot by the way?) so I shut her down. Looked at the coolant reservoir and it was bubbling/boiling. Everything including fenders were hot to the touch.

There is no water/coolant in the oil, it doesn't smoke, the fan spins freely, the radiator is full still. Under normal driving it does not overheat.

I have a radiator on order... it arrives tomorrow.

 

What's the temperature outside? And it got hotter then 210 going uphill? Sounds normal to me. As long as it doesn't go above 220 degrees

 

Uphill it was night time so around 65 degrees, right now when I had it idling it was about 70 degrees. The bubbling in the reservoir is normal? after idling?

 

As long as you're popping in a radiator, consider installing a new water pump, a new thermostat and a new radiator cap. Now is the time to do that while you have the cooling system apart; the parts are not that expensive. Check condition of all coolant hoses.

If one cooling system component is failing, often others are not far behind. No better money spent on maintenance than that spent on the cooling system.

 

Based on your "solved" I just went and got a 16# cap as well. Mine is running hot too. can someone explain why a cap would make a difference how hot it runs?

 

Quote:

Originally Posted by Rockchalk

Based on your "solved" I just went and got a 16# cap as well. Mine is running hot too. can someone explain why a cap would make a difference how hot it runs?

Google is a search engine. It finds things for us. Use the Googles.

 

Google smoogle... thanks for the tip

 

Quote:

Originally Posted by Rockchalk

Google smoogle... thanks for the tip

heh, np. I couldn't resist being a smart-*ss ; it rained on the only off day possible for me to take my JKUr out to rock garden after installing RCVs in her last weekend. That means I get two or three weeks of work across the country before being able to wheel...I am in a p*sser today.

that links to the alpar pages* which I have found very , very valuable since it is all Chrysler engineers and the discussion about our vehicles with their input. You're welcome, mate. No hard feelins....?


{*specifically the pages at Alpar regarding caps for the radiator }

 

Linky no worky... I'll see if I can find it on my own. Trust me... I have spent hours doing searches and watching videos. No worries and blue skies. Sorry for the de-rail OP!

 

http://www.allpar.com/fix/engines/cooling-caps.html