Novak Conversions Jeep Wrangler JK radiators

Overheating

Electric Banana

New Member
Joined
Mar 29, 2026
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1
Location
North Carolina
Evening to all. Just picked up a 2015 Jeep Wrangler Unlimited Sahara, and I'm hoping that I didn't inherit someone else's headache. After purchase drove it 2 hours on highway to get home. Next day drove another 2 hour round trip with no problems. Ran heat and AC. Next day drove to work and turned on heater and it started to overheat. It would heay up to thhe point of warning coming on after parking the temp would drop back to normal. Short of it had to drive and stop all the way back home. Tried the burp the system and all I got was antifreeze back flowing out. Took to mechanic and he replaced the thermostat. Ran fine for a week and a half and started again. My mechanic thinks its a head gasket. but he didn't do all the tests. I'm going to perform a block test and then a leak down. If these prove negative might it be the wart pump? I did notice that after a week of sitting there was still pressure under the radiator cap which I don;t think is good. Looking for ideas and suggestions.
 
You need a scanner with live data. What’s the temp reading off the scanner?

Also, if your electric fan isn’t coming on or gradually failing, it would overheat most likely. Outside temps would be good to know as well.

Pressure is created by the expansion of the coolant when heated. The water pump really just moves the coolant around. It doesn’t create pressure. If it’s maintaining some pressure after being shut off for awhile, that means you don’t have a leak.
 
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There should not be pressure after a week of sitting! Honestly, after 12 hours there shouldn't be pressure. It's either a head gasket leak or a cracked block from it overheating. Have you looked under your oil cap for any light colored chocolate milk?
 
Novak Conversions Jeep Wrangler JK radiators