I need help. I have a 99 xj limited. I have replaced all of the hoses, thermo, water pump, temp sensor, new fan clutch, electric fan, and shroud. Short of a new radiator, the whole system is new. I have done a good flush of the entire system. No leaks or blocks. It drives good most of the time, but on longer drives it overheats. It will run at normal temp, and then jump instantly up to 250. It sits at 250 for a bit and then goes back down to 215. The jumps in temp happen quick, it goes up in a matter of seconds. I thought it may be a short in the guage but today it jumped up and continued until it actually overheated. I tried a good burp on the system, but I have done that before and the short bursts of overheating continue. What gives? Is there a special way to burp it I don't know about?

 

Any chance the radiator is blocked? Both hoses getting hot?

195 Thermostat?

Ant...

 

Have you turned on the heater and cleaned the core on it, then checked to see if hot water goes in and out. The temp control inside needs to be on high and engine hot.

What did the water/antifreeze look like when you drained it the first time? What does the inside of the radiator look like when you shine a flashlight into it?

 

Why r u hesitant to replace the only cooling system component (the rad) that actually dissipates heat? Just because flush water flows in and out of the old rad doesn't mean the tubes are not coated internally with scaly crud reducing heat removal efficiency. U cannot see inside a XJ rad.....only way to tell if it's crudded up is to have a rad shop separate the tanks from the core.

 

^^This!^^