benhockeypl1

I have a 1989 Cherokee with 4.5 lift and 33" tires. I upgraded to the newer cooling system years ago (got rid of the pressurized overflow and no radiator cap set up). 2 weeks ago I was going up north and it was about 3am I had the windows down and the ac off cruising on the freeway and my jeep started getting hot. I live in phoenix and with out the ac on it runs a little over 160(I have a 160 thermostat) and with the ac on it runs about 200-210. well it overheated and I let it sit for hours then came back and pulled the t stat but it was good. filled it up and tried to make it back to town and within 5-10 mins it overheated again. I had it towed and I pulled the water pump ( hesco billet high output water pump) and it looks great, spins freely so its not that. I have a all aluminum radiator that's just about a year old so I know its good. took it to the local mechanic that's a family friend and he is pretty much stumped too. all my hoses are good none are weak, im not leaking and the system is holding pressure. I drove it again the other day and sure thing within 10 mins it was at 260 degrees. im stumped, if you guys have any advice please let me know. I have checked everything I can think of and even a mechanic spent 3 hours looking at it and couldn't give me a explanation. thanks a lot in advance!

Firestorm500

We had a post just about like this a couple of days ago.

Once again, you have the classic signs of a blown head gasket.

djb383

......and the dash gauge reading has been verified?

aroundincircles

blown head gasket/plugged exhaust.

benhockeypl1

Yes, the gauge works because it does overheat. If it was a blown head gasket wouldn't there be antifreeze in the oil? The first thing the mechanic did was check and smell the oil for coolant but found no signs. What's this plugged exhaust theory? That seems interesting due to it has started randomly back firing in the manifold at low rpm's a few times

Ant.

Sounds like the head gasket to me..

I had same problem with my 99 cherokee.. I could run the jeep all day in the driveway with no issue/ and around town, But as soon as I got on the freeway all my coolant was going out the exhaust.. The head was cracked


Ant...

Firestorm500

You need to get a more experienced mechanic.

It is either blown between cylinders, or the head is cracked. Or both.

Don't let him do anything else to your Jeep, if you know what's good for you.

stitch702

Compression test it and post up the results

95Cherokee

A test to see if the head gasket has blown or not, is to remove the radiator cap and then crank and/or start your Jeep. What this test will confirm is if the head gasket is letting engine compression into the cooling system (radiator) or not.


Do this with a cold engine

1. 
   
   Remove the radiator's cap. If the radiator does not have any coolant, add some water
   
2. Crank the engine.

If the coolant bubbled out or shot out from the radiator: This is not good and indicates beyond a shadow of a doubt that the head gasket is blown on a Jeep 4.0L Cherokee.