Buckn63

I have a 1999 Cherokee Sport with a 4.0l 6. About a month ago it started overheating when driving around town and on the highway. I got into my busy time of the year and I didn't have much time to look at it. My fiance took it to a local garage and they told her that it was a head gasket and it was going to cost 1500 to fix it. I don't know what test they did to diagnose the problem. She said they were being kinda crappy about the whole thing. They didn't mention anything about the cooling system.

There is no white smoke from the exhaust and the engine sounds normal when I start it. The guy at the auto parts store said the jeep 4.0 was a pretty solid engine and that it is pretty tough to blow the head gasket. He also said the problem is usually in the cooling system. He said Thermostat or Water Pump were probably the problem. It seems to run fine other then the gauge going all the way to the red when driving it. Starts normal and sounds like it always has.

Earlier in the summer I added some 50/50 mix because the overflow tank was empty. The coolant now looks like chocolate milk but is at a normal level in the tank. When I opened the radiator cap there was an orange crud around the inside and on the cap and I couldn't see any fluid. It looks like the cap is off to the side and not right over the radiator. I have no Idea when the last time the radiator was flushed or what it was filled with before.

When I started the car and looked in the overflow tank there were a few bubbles coming up thru the coolant that was in there.

My initial plan is to flush the radiator and change out the t-stat. The more I read the more I'm concerned that i may have mixed coolant types and gunked up the radiator.

I also may change out the water pump but I'm not 100% where it is or how I get to it. They say its easy to get to.

I'm working on the cooling system because I wont have time change a head gasket until November. I'm also hoping that it isn't the gasket.

I have limited mechanical ability but I have been able to figure out how to fix some things after looking at this board and doing some internet searches. I have some time this Sunday that I plan on using to work on the Jeep.

I'm looking for advice on what steps I should take and if there is anything else I can do to help my jeep. What is the best way to flush my radiator? Should I use a chemical flushing agent? How should I empty it and what should I fill it with when I'm done? This would be my first time working on the cooling system so details / diagrams would be helpful if available.

On another note. If it is a gasket issue has anyone had any success with a product called blue devil gasket sealant?

Thanks in advance!

AirborneDeth

The gunking problem 'probably' is because of mixed coolant. I would start by flushing the entire cooling system really good, along with a new Tstat and water pump. This may be a good time for new hoses as well.

Mr2Jeep

I recently had a similar problem. Mine was overheating too so I started with the thermostat because it was the cheapest part and easiest to get to, that really didn’t seem to solve the problem. Next was the fan clutch that made a big difference in lowering the temps. During all the overheating problems I developed a leak in the radiator, it was the original so I guess it was time to go. While I had the radiator out I replaced the water pump too. So now I’ve replaced the Thermostat, fan clutch, radiator, water pump and new radiator hoses. All is good now.

Buckn63

Right now I think a flush is needed and I already have the t-stat. Does anyone have any advice on chemical flushing solutions?

car5car

If you have bubbles in coolant bottle, you probably have gasket problem.
You can smell exhaust gas in the bottle.