HI there, i have a 99 xj sport it has been overheating so in the last few weeks i have replaced

rad
thermostat/housing
water pump
all hoses

and flushed the living crap out of the engine "crap" is a understatement.
the fluid was gunky real gunky. now it seems to only over heat when idling and the heater is on. the only thing i haven't got around to yet is the heater core which i suspect is causing my issue because the heater only blows warm air not hot, also another suspicious thing is the a/c lines become wet with condensation only when the heater is on i don't know if this is normal or not. i also tested the fan and blending actuator all tested fine. so my questions are.

if the heater core is bunged up would it cause the engine to overheat?

are the a/c lines supposed to become wet with condensation when the heater is on?

might there be anything else i am missing?

thanks

 

If you overheat at idle it is likely your fan clutch. Also, why do you have thever heater on with this heat hahah

 

/thread.

But also...

If your heat is lukewarm, you might want to try backflushing your heater core. That's not likely to have anything to do with your overheating issue, but it might help you get more heat for your deep summer driving comfort.

 

Thanks martlor I will check out the fan clutch. I live in Canada we always have cool mornings haha

 

Nice, its so hot in south texas right now even an engine that hasn't been on in 24 hrs will have a starting temp of like 160 degrees LOL.

with the engine off obviously, try turning your engine fan. Does it Freely rotate or does it have resistance. I heard thats a good way to test a bad fan clutch.

 

That test is not reliable. The only reliable way to test a fan clutch is to take it off the vehicle, rotate the spring 180° and lock it there so that the clutch is always engaged, reinstall the fan clutch and see if the overheating issue goes away. If it does, you have to take it off again and replace it. If it doesn't, you still have to take it off and put the spring back where it's supposed to be.

The fan clutch is $35-$40, but the symptom of overheating at idle is usually a pretty good indication that the fan clutch is bad. Unless you're really strapped for cash and can't come up with $35, by the time you go to all that trouble you might as well just replace it when you take it off the first time.

 

I haven't had a mechanical fan for a year and a half or more now. Sitting at idle on a 90 degree day it will go slightly over 210. Maybe even 220. But when the electric fan kicks on it will drop the temp and eventually the e fan will kick off for a minute before kicking back on. I have yet to overheat it or even come close. Did a flush, water pump, t-stat and housing,heater tube, hoses and installed a used non leaking radiator from my parts jeep last fall. Now my heater core is partially clogged so I need to back flush that before winter. Sucks that so many others have cooling problems somehow. Anyone ever checked to see if they're running lean or something when they have overheat problems after installing a whole new cooling system? Seems like hotter combustion temps could be a possibility.

 

I have same results way erd. If im cruising doen road my temps are slightly below 210. If im idol at a light for a long time or drive though it will be slight slight slightly over 210. When i first got jeep it was using a mix of who knows what coolant. Cooling system performed way better after doing flush!

 

(Post deleted because I haven't had coffee yet this morning.)

 

Hey guys thanks for all the input. The fab clutch is good I parked the jeep on a bit of a hill and cracked the rad cap a ton of bubbles came up. I guess I didn't burp it well enough. She runs at a steady 210-215. The heater still only blows like warm I am going to try and back flush it a few more times to see if that helps. But the main thing is that it's not overheating anymore and the coolant is bright green not the sludgy brown it was