Overheating 90 cherokee

Hey all :bananasmi

I am the proud owner of a 90 Cherokee Larado and this forum is GREAT :thumbsup: It has the 4.0l inline 6 and i cannot wait to get it back on the road :biggrin:

The problem i am having is overheating while ideling......

I have been reading the overheating posts now for a couple of days and have tried the bruping of the system to no real benefit....a ton of air escapes thru the sensor location in the head.....the jeep behaves for a few mins then wham the temp hops up to over 230 and the system starts to force water out the pressure bottle.....the raditor is a tad warm but not hot....but the water is pouring out the pressure bottle....at first i had a cracked bottle and a stuck t-stat, replaced both but still overheating......and yes the t-stat has the little hole with the ball bearing in it to releave the air pocket.....WHERE DO I GO FROM HERE?

Also i ran a can of radiator flush thru the system and the water came out pretty clean :feedback:

Thanks

Chili

You're sure the water pump is working...? When I ran radiator flush through mine not long ago, it took the seals out of the pump, along with the other gunk. An overly hot engine but a "tad warm" radiator tells me you're not circualting water...
Just a shot in the dark.

Idaho has a good point, look at your waterpump, then also remove you radiator and get it cleaned. It could be clogged up, also, when you installed the T-stat, did you make sure that the little ball bearing was at the TOP of the T-stat when you installed the housing?

Idaho has a good point, look at your waterpump, then also remove you radiator and get it cleaned. It could be clogged up, also, when you installed the T-stat, did you make sure that the little ball bearing was at the TOP of the T-stat when you installed the housing?

Thanks will chek the waterpump and i am sure the hole is pointing up.

Thanks again

Chili

If the coolant is surging out of the overflow tank like that, its very possible you've got a leaking head gasket. Try a compression check on the cylinders and look at the spark plugs when you pull them. A sure sign of a head gasket leak is one plug that looks a lot cleaner than the rest. Even if you don't see a serious difference in pressure or plug color, I would still suspect the head gasket based on your symptoms. A cracked overflow tank can be caused by the excessive pressure build up a leaking gasket can cause.