cubanchris81

I have a 98 XJ 4.0 drivin on highway about 70 mph it overheats temp gauge was readin 250° then as if thermostat opened up temp started falling. I replaced t-stat got on highway again & same problem. I bought a superstat thermostat so I removed it & went back out that night no problems even at 95mph. Next trip on highway during the day same problem with no t-stat so I check radiator & it has cold spots so I ordered a new 1 from dpg their CSF 3 row be here this week but is there anything else I should check/change with new radiator? To me it didn't sound like a radiator issue but cold spots means poor circulation its just wierd how my Jeep got so hot for several minutes then drop suddenly like a bad t-stat.

DuckrazeeXJ

Had mine do that a while back. Mechanic told me that if the fluid levels are low, an air bubble in the thermostat can cause a false high temp reading. Filled mine all the way up, started it, and kept fillin till it was completely full, never had the problem again.

cubanchris81

I double checked today ran jeep reving engine & all only thing it did was start to overflow once warm. But I'm not runin a thermostat I took it out thinking that was problem so there's no air but I was talkin to a buddy & his jeep did same thing was radiator mine should be here this week see if that does it.

Tural

99% sure it's just the radiator. but in order for the radiator to be stopped up, there has to be a lot of trash in the lines. i would suggest taking out the thermostat, hooking up a water hose to the heater core hose and letting it run for about 5 min. then start the vehicle and let it circulate while the vehicle is running for another 5 min. so far i've found that out to be the best way to flush, because you can buy hose fittings at the hardware store that will hook right up to your water hose. other people might have a different way of doing it. just make sure you're in the ditch when you do that because the water is gonna come out right from the goose neck and it's gonna kinda go everywhere. btw, this is to be done with your old radiator. you don't want all that trash running through your new radiator.

fishtaconc

you need the restriction of the tstat the without it the water moves to fast through the radiator to loose the heat, also this will cause cavitation within the cooling system