we have a 90 jeep Cherokee 4.0 liter it has new engine, all fuel system new , a new header , fans are new, t stat , a/c new, and after driving 5 minutes it hits 245 but no boil over, we wrapped header to disapate heat , scan tool shows good fuel trims , not sure what is going on any thoughts ? we have tried different fans and t stats and checked time but still runs hot. nothing changes temp and coolant is that hot. installed 2 loovers in hood to let heat out , thank you for any help

 

Maybe you should remove the thermostat for a test. It sounds like if it's not opening at the proper temperature.

 

Radiator blockage? 5 minutes of run time is really quick for it to reach 245 degrees. Plugged up exhaust? Blocked heater core? Are you getting coolant flow?

 

I installed a new 3 core radiator , and factory stat , it is working , heater core is new thinking about pitting it under hood with fan on it , tested everything from fuel , timing , flow, weter water , and wrapped exhaust, last trip I took off hood and seemed to bring down some last temp was 228 with hood off and a/c on but still is hotter than I would like. new jasper engine 1st one we thought possible crack between valves and replaced with another new jasper eng. still runs hot , un caped header and ran with no exhaust and no help, hood off did the most, im thinking core out by bumper with fan maybe will help then I thought maybe an electric water pump to movee coolaqnt a little faster, when you coast at 50mph then rev engine in neutral it also drops a little, maybe coolant not fast enough with out t stat it gets hot so that's too fast of flow, just really baffeled after 49 years of working on cars this one is a brain teaser.

 

So other than your gauge showing it's overheating no other symptoms? If not get hold of an infared temp gun and check up around the thermostat housing to get verified temp reading.

 

Makes no sense to me...

Sounds like there is blockage somewhere, Engine should definitely not run at 228, Well I don't know to much about the 1990

I have a 99 and it runs at 205 when moving and when sitting it hits 210, But thats it, Never goes over that.. I have a new engine as well and if it ran at those temps I would not be happy and would for sure find the problem b-4 driving it..

Ant...

 

If that temp is from the temp gauge don't trust it factory gauges can read wrong high or low.