Krystle

I have a 1990 Cherokee that I just purchased at the beginning of July. I am having terrible overheating problems. I first changed my radiator cap, it was bad. Then at the beginning of Aug, my tags were expired and I had to do emissions. It didn't pass the first couple of times. I replaced the fuel injectors and cadillac converter. It passed emissions. I then decided to changed the water pump, thermostat, serpentine belt, and spark plugs. The hose to the reservoir overflow was leaking at the end, so that was replaced. It ran extremely well for about a day. Today on my way to work, it started getting hot again. It was in between 210 & 260 <--- overheat.

What else could it be? I would imagine that the garage I took it to pass emissions did a pressure test, that is why they had to replace the cadillac converter. This leads me to believe the head gasket is fine. Would that be a good assumption?

If all of these things have been replaced, what else would cause it to overheat like this?

kirknd4spd

Assuming its got the 4.0, did you get all the air out of the cooling system? If its got the 4.0 it should have a closed cooling system...but you said you replaced the radiator cap? Shouldn't have a cap on the radiator.
What kind of shape is the clutch on the fan in?
And again, assuming it has the 4.0, does the electric fan work?

Krystle

This is a 6.0

kirknd4spd

6.0 in a 90 XJ? Engine swap? What kind of 6 liter engine?

Krystle

Wait, you just lost me. It's a 1990 Jeep Cherokee 6 cylinder.

kirknd4spd

Ok, so you have the 4.0. 4 liter inline 6 cylinder.
Refer to my first post then, that's a few things to check out pretty quick and easy.

Krystle

You say that I should NOT have a radiator cap? It does look like they have replaced or done some work to the radiator. Hmmmm.....

Thank you for your help. I am going to check the fan after my long drive home from wor

kirknd4spd

Yeah, it shouldn't have a cap. Should have a bottle on the passenger side at the firewall to put coolant in.
Sounds like its been converted to an open cooling system. Not a big deal, I personally prefer open systems.

peterk

What years lack a radiator cap? My 1996 4.0 six has a radiator cap. In my case, it is important that the air be bled from the cooling system after any maintenance. Always takes me a few cycles. I'd advise removing the cap after the engine is cold, and making sure the radiator takes absolutely no water.

PocketsEmpty

Did you do a cooling system pressure test?

cruiser54

87 to 90 had no radiator cap.

Bleeding isn't important on an open system with a radiator cap and not a big deal on the closed system either.

BlueXJ

Bleeding air from a Renix (87-90) is harder to do but is essential to have proper cooling.

cruiser54

I'm gonna have to respectfully disagree.

As Service Manager and Shop Foreman at a Jeep dealer from 1980 through 1992, I can assure you that from 87 til 92 neither myself or any of my Techs ever bled a Renix Jeep cooling system and had absolutely no issues. This includes not only all water pump, hose, thermostat replacements, but the recommended chainging of the coolant every 22,000 miles.

Check this out from the FSM

This system does not have a radiator pressure cap. Instead the pressure cap is mounted on the coolant pressure bottle. System coolant flows directly through a fully pressurized Hot-Type expansion bottle. Coolant flows through the pressure bottle at all times during engine operation whether the engine is cold or at normal operating temperatures.

Larger coolant volume caused by thermal expansion during engine operation is absorbed by the expansion chamber in the bottle. Air trapped in the system is purged through the pressure cap vent valve during maximum coolant expansion..

peterk

Thanks for explaining that 87-90 have no radiator cap. Sure enough, I verified that by looking at pictures on a very cool offering on eBay motors.

Even after seventeen years of owning my '96, I still get confused when I fail to bleed all the air. When I change the coolant, my test to see that the cooling system is working is that I get a good, strong flow of hot air out of the defroster. It requires a good two or three warm-up / cooldown cycles in my case to get good defrost, even though I jack up the front, squeeze the return hose, etc. As we all know, running the defroster proves you still have water, that it is flowing, and also adds some cooling capacity, though just a little.

Sounds like you are more patient, waiting for the air to bleed. I guess I am hyperactive, and want the defrost to work on the first warm-up.