jkujonnyb

Hi y’all, I have searched online and read through a bunch of posts but can’t seem to find the same issue I’m having. So here’s the deal, sometimes the Jeep will run around 210-215 and the temps will drop (functions normal) then it will shoot up to 230’s then come back town to around 215 or so. Few and far between it will clime up to 240 then drop back down. I can hear the fan screaming when it’s over 230 so it seems like the fan is working properly. Almost seems like the t-stat is sticking but it is opening. Checked for any blockage and I don’t notice anything. No debris. Fins are clean.

The radiator is holding pressure indefinitely. I will park the truck for hours, even overnight and there is still pressure in the radiator. Also the antifreeze goes into the overflow tank but it always just stays in the tank. It’s always full. I suspect because of the pressure.

The oil is clean, there’s no white smoke coming out the tailpipe, I haven’t seen any bubbling inside the overflow or in the radiator. I haven’t changed the tstat yet but I will soon to see if that may be the problem but I really don’t think that is the problem. It’s cheap and easy to do. Just trying to diagnose before throwing parts at it. But I’m kinda at a loss with this pressure issue. If it was a head gasket are there any other symptoms I might notice? Thanks in advance
JonnyB

XJRefugee

IMO you have nothing wrong. Your observations are showing you are paying attention to what is happening to your JK. Everything you describe has happened to my jeep also. 230 degrees is sustainable on the 3.6l engine and as long as it returns to 210-215 without turning to steam , you are fine. All these modern engines run warmer than what we were used to in the past. The antifreeze used today has a much higher boiling temp. than the older stuff so your engine is protected at those higher temps because the coolant has not turned to steam. filling the overflow bucket is normal as long as eventually it all returns to radiator.