Ok I have a 91 cherokee 4.0. New to me 130k engine out of a wrecked 98 ZJ ( old engine had a scored block after overheating by the PO ) New water pump,thermostat,clutch fan, radiator and hoses. Also new sensors. It still gets hot, around 220-225 before I shut it off. No coolant in the oil that I can see but there is moisture on the oil cap. Compression test puts all cylinders within 3-5 lbs of each other. Small amount of moisture coming from the exhaust. Any Ideas?

 

Is the coolant recovery system working correctly? New rad cap? Fan shroud in place? Coolant temp verified with infrared temp gun? Run hot at hi-way speed or slow/no speed?

 

Fan shroud is in place. I haven't tried to drive it yet, it overheats just sitting in the driveway. I haven't used a temp gun, but you can hear the coolant boiling when you shut it off. No new cap I'm getting that today. I assume the recovery bottle is working correctly. It doesn't boil over into the bottle.

 

The rad cap is the key to the recovery system as the cap is a 2-way valve.....releases air from the rad as the motor heats and allows coolant to return to the rad as the motor cools. The bottle MUST ALWAYS have some coolant in it, otherwise air is sucked into the rad when the motor cools. Make sure the rad is staying full, MOTOR COLD.

 

Since you are going to pick up a new radiator cap you should also pick up a new thermostat too. Make sure it is a 195deg.

 

I believe it's all new (except for the rad cap)......that's what's puzzling.

 

It wouldn't hurt to change out the t stat since you didn't change it out yourself. Did you recheck the fan clutch yourself too? If not, you should.

 

Thanks guys for the help. Everything is new except the rad cap. Just put a new t stat in yesterday with the new radiator and fan clutch, still over heated. That's when I posted for your guys help.

 

Just keep us updated on the out come.

 

Check your serp. belt routing. Also, did you get a temp sensor for a 98 ZJ or 91 Xj? I'm not sure if there's a difference, but it may be a different temp range on the ZJ. Definitely verify the temp if possible. And replace that cap.

 

Double check that the cooling system gets bled thoroughly. Took bleeding one of my Jeeps like half an hour to an hour before all the air bubbles got out and also make sure the heater is on full when doing it.

I had replaced nearly everything in one of my Jeeps and only burped the hoses for like 5-10 minutes and thought it'd be good, only to find it was overheating still.

Confused, I re-burped the system and it fixed it. :P

 

He has a 91, which would be an open cooling system. Otherwise I'd agree.

 

I put in a temp sender for a 91. The pic is after the new cap. Still to hot? And my electric fan isn't kicking on.

 

How quickly is the temp getting up there?

Could still be air in the system. Does the coolant level in your bottle change at all after cooling down. As in, check it when its cold then again after you warm it up and let it cool down.

Mine ran a hair high like that but the heat up/cool down cycle sucked more coolant in as every little bubble of air was displaced.

 

That appears to be 220ish.....would think the efan would be on.