Okay just picked up a 96. 4.0L auto. When I test drove it, it was getting warm (almost in the red). I saw the water pump seeping so I figured water pump. Now this jeep has never been off road. One owner and no mods nothing.

So I got it home and did the normal things Changed all the fluids. I then started tackling the overheating issue. Total system flush, New: T-stat, water pump, fan clutch, radiator cap, flush and tested radiator all good. Electric fan working great.

Started it up and Still overheating. So changed the Temp. Sending unit: Still overheating. So put an external temp gauge on it and 210. So I figured I was done. Oh but No I got in it 2 days later and drove over to pick the boy up and started over heating again (235-245)

Does not matter if I am driving or at Idle. So I figured I would start another overheating thread (sorry) Because I am about to pull my hair out over this one.

Any suggestions?

Thanks Mark

 

oil in coolant or coolant in oil would be symptomatic of a head gasket issue

 

you for got one more sign of head issue bubbles going into coolant bottle would be exhaust gasses getting into coolant passages

 

Does it heat up fast?

I had a similar problem once where it would overheat after a few minutes of idling and wouldn't stay cool no matter what i did. Long story short the head was cracked between the valves and a bad temp gauge in the dash. I figured out it was a cracked head from running the jeep with no coolant in the system at all and upon opening it up, I found alot of pressure had built up. Even afterwards the guage would act funny and it turned out the connections were all cracked up. Found just the temp gauge on ebay for like $1

 

No oil in the Coolant and No Coolant in the oil.

I am leading toward a head issue my self. Isnt there a test you can do to test for exhaust in the coolant?

No bubbles in the coolant jug.

 

If you suspect a head gasket problem, look for fluffy clouds of steam coming out of the tailpipe, you would also feel a miss at idle. Take the electric fan and mechanical fan shroud off at the core support and remove the core support. Look between the radiator and condensor for debris such as grass, dirt, feathers, leaves,ect. I bet you'll find a lot of crap in there.

 

See thats what blows my mind. I have nothing coming out of the tailpipe. I have nothing around the radiator has I removed the radiator (whole front end) when I flushed and tested and replaced the cooling system. But I do have a miss at idle

This is why I am frustrated.

 

Not sure what "tested radiator" means. The rad may not leak but it may not be dissipating heat adequately either. Only one way to check for scale build-up inside the tubes and that's to have a rad shop remove the tanks and inspect.......or skip that and replace the rad. If I'm reading correctly everything u have replaced, replacing/inspecting (internally) the rad is the only thing u haven't.

 

You are correct. I press. tested it and had it rodded (just to be sure).
I should be able to do a pressure test and tell if the head gasket is blown, will this also tell me if the head is cracked? If it checks out with compression then the rad. is the only other thing to replace.

 

If the rad has been rodded, it should be good as new. The only exception would be, did the rad shop block/seal any leaking tubes? The XJ rad is just about as dinky as they come and needs ALL of the tubes flowing to the max.

 

Not to my knowledge. But you never know LOL. I am going to go out and do a compress. test and see what it look like. I will report back. Thanks for the input guys.

 

Okay so compression

Cyl 1 : 170
Cyl 2: 165
Cyl 3: 165
Cyl 4: 165
Cyl 5: 165
Cyl 6: 165

Does this raise any alarms to anyone?

 

.......if your coolant temp was only 170.

 

Correction Cyl 5 was 135 ..... Sorry allergy meds !!

 

That raises an alarm.