Hopefully you Cherokee experts can help me figure out a weird problem.

I dropped a long block remanufactured engine in my 96 4.0, last one blew a head gasket.

-Heater works great
-Upper radiator hose is cold
-Engine overheats after several minutes

I thought this to be symptoms of a bad thermostat, so I replaced it and still the same results.
I flushed out my Performance brand radiator which still seems in good shape, installed a TEE in the heater hose and back flushed the entire system and still the same results.

Could it just be air pockets in the system or could this be a water pump issue or something else entirely?

 

For all that you've described and done so far, sounds like you may need to investigate the water pump. Assuming too that the air is gone from the system, first.

 

My 96 was doing the same thing until the head cracked and it threw a rod. I also did what you described plus changing the water pump. None of it helped. I am installing a new engine in mine because the old one is no good. If mine continues to overheat after it has a new engine my next move is to replace the radiator.

 

I can't remember if my new engine came with a new water pump or if I put the old one on there. It doesn't seem to have a drip at the bottom.

 

Thermostat installed backwards.

 

X2 upper hose should not be cold even with a clogged rad or air in the system. Also new tstats straight from the box can be bad. Ask how I know.

 

Am I right in saying only closed cooling systems have issues with air in them? I know the '96 is an open system.

 

Show me how it's possible to install a thermostat backwards on an i6 with the stock thermostat housing...

 

x2, you'd be amazed how many are bad out of the box. I finally had to buy one from the stealership.

 

I take it you tried and couldn't install it? I know better.
I'm just guessing, kinda strange to have two defective thermostats in a row. I guess we will see for sure when the OP returns.

 

Deff agree in bad thermostats cuz ppl buy the cheap 4 dollar ones... Buy the expensive fail save plated ones yet to have one fail.. But cheap ones very common to failure! Or u did put it in backwards and are leaking lol..

 

No, I just know it will only fit in one direction, the thermostat housing is too small to put it in backwards.

 

"fail safe" thermostats are crap. If they open far enough they have a latch that prevents it from closing.

 

It's better than ppl buying cheap ones and over heating there engine! Right!? I just buy the good plated ones from napa non fail safe.. Like 10 bucks give or take..

 

When I was at NAPA, they acted like the six dollar one I bought was the only thermostat they had.

I know I didn't put the thermostat in backwards. I triple checked to make sure it was facing the right way.

Tomorrow, I'm going to take it back out and see if it opens up in a pan of boiling water.

I should have bought a six pack of thermostat gaskets!