ncaskets

I have an 88 cherokee laredo in-line 6 (242c.i.d.), automatic, lifted w/35's that overheats!!! I have replaced the T-stat, water pump, electric fan, mechanical fan, coolant temperature sensor and all hoses but it keeps overheating. It has a sealed radiator and must be filled through overflow tank and by removing top radiator hose and filling directly into radiator. Can anyone help me?!!!!!

MjPioneer

Try a new radiator, also try a new pressure bottle.

ncaskets

Cool, thanks!! On the overflow tank there is a brass valve with internal threads, what's this?

XxXJ99xX

And another problem would be air locks in the cooling system. I had one in my jeep and almost blew it up after the stealership worked on the ac/heater system. Make sure yours dosent have one because if you keep replacing parts then itd make no sense. Also check your head gasket.

myjeep

what ive always done when i worked on cars back then is take out the colant sensor on the back driver side of the head, then fill the coolant until it pisses out there and no air bubbles are comming out. then as it is still pissing put the sensor back in then fill the bottle. then run til the t-stat opens up then it is good. never had a problem after doing this.

i even did this with the lt1 camaros and firebirds as those engines are reverse rotation cooling systems to, they suck air in.

ushersxj

Overheating is a common problem with the earlier 4.0 xjs. It was normally caused by air pockets in the system that is why jeep changed the design on the later models. I had a 91 xj that did the same thing and added a spliced in plastic tee with a cap on top inline with the highest heater hose on the engine. after the t-stat opened and the cap off it would allow all air to escape being that it was the highest point in the cooling system. Also it would be a good idea to have the radiator rodded out and pressure test the resivour bottle.

Willys55

very good advice, I do the same thing.

Check your engine for a head gasket issue as well.

redrunner

You can put in an inline rad fill cap in the upper rad line, put in a standard over flow bottle and pitch that rotten plastic bottle that cracks, leaks and won't hold pressure. This will change you from the closed system to the open system. Do a search and the step by step instruction are other there. This is a very simple fix for one major problem with Renix engines.

harley5940

Check your coolant for air pockets also take a pressure tester to your cylinders and if one reads lower then the others then you have a blown head gasket.

Austin Boylan

After all of these amazing suggestions, your Cherokee may still "over heat" in the summer, and radiator may need covered in the winter (depending on vehicular use) because it's not running hot enough 🤣 It's a nature of the beast that you get suckered into knowingly 😍😍😍 It tends to do the opposite of what you'd like. When needed, she will be the star of the show in multiple aspects ⭐📽️. Aluminum warps at 220°-ish fahrenheit, and I would personally say don't be afraid of pushing 210 as long as you watch the guage, even with a stock closed cooling system. I run a factory 195° thermostat, hours-long highway temp is 215 steady and she loves it.

Chick-N-Picker

If your going to get a new radiator then go ahead and get one for a 91 to 96 and change to the open cooling system.

And always make sure you fill with your heater on and on high. If it's off in will cause air to be in the system.

Saudade

Considering the OP is from 2010 and hasn't been back since 2011, I assume he either fixed it or dumped it.

Chick-N-Picker

^ Yeah, the person before me posted today so I just fell in line...dang they finally got me.

awg

Eleven years and 2 months is the oldest zombie reply I can recall on this forum

Outstanding

did see one OP reply to a 5yr old revival !