XJ Coolant Problems

So I have a 1990 Jeep Cherokee with the Renix engine and a closed cooling system, lately I've been having over heating problems. My temp gauge would sometimes randomly raise above 220 and begin to over heat whether I've been running it for 5 min or an hour, there really hasn't been any consistency, and often(but not every time) when it over heated the radiator cap would either burst off or come loose and coolant would spill everywhere. I've some friends mention that if there's a crack in the reservoir that could be causing it, and I should replace that. I've also been told that maybe my electrical fan isn't always turning on when it's supposed to and I should just put it on a switch. I've already lifted up the back of the hood to let hot air escape, but I'm wondering if you guys might have another theories or suggestions as to what I can do?

How's the radiator look? Have you checked out the thermostat ?

When it runs hot is the fan on?

piginajeep said:

How's the radiator look? Have you checked out the thermostat ?

When it runs hot is the fan on?

Click to expand...

He washed out the radiator a little bit ago... it could probably use replacing/refurbishing.

The thermostat ... there wasn't one when he bought it. We put one in it and it seemed to help but then it started to get worse so we took it out to see if it would help.

That is a good question it seems to be 50/50. We are going to put the electrical fan on a switch so we can turn it on and off manually see if that helps.

NAUJK said:

He washed out the radiator a little bit ago... it could probably use replacing/refurbishing.

The thermostat ... there wasn't one when he bought it. We put one in it and it seemed to help but then it started to get worse so we took it out to see if it would help.

That is a good question it seems to be 50/50. We are going to put the electrical fan on a switch so we can turn it on and off manually see if that helps.

Click to expand...

One other thing, did he burp it to make sure there's no air pockets in the water system? In the back of the block is a valve to open up. The way the motor sits the back end needs to be up in the air so the motor sits level.

Yeah I did make sure to burp the jeep while facing down a hill, but I burped it using the radiator cap on the reservoir, which is the highest and furthest back part of my coolant system that I know of.

The XJ I had with a closed cooling system had a split in the top seam of the radiator, and at a different time also cracked the coolant bottle. It also had random overheating problems. Unfortunately (or fortunately) I sold the 90 before figuring out the problem. I bought a 91 with an open system and it never over heated.

I've heard of people swap out the cooling system to a 92+ open system (or one made in latter half of 91 when they switch over), but I don't have any experience with using this as a fix.

Be sure you don't have a blown head gasket. That can also cause similar symptoms.

I'm fairly positive I don't have any head gasket problems. I'd like to eventually swap out to a 92+ coolant system, but at the current moment I don't have the money to do so.