Intermittent Overheating

[TJBart]

Hello

I have a 1999 Wrangler with the 4.0L and Automatic Transmission. I have been having an issue with intermittent overheating over the last week. I have had this jeep since Christmas, and when I bought it the thermostat was stuck open and it ran very cool. I replaced the thermostat and it ran fine until I took it 4-wheeling last weekend and it overheated on the interstate on the way home. I figured it might be the thermostat sticking closed so I replaced it again but it has overheated 2 or 3 times over the last week. The car will normally run slightly over 210, but occasionally it shoots up into the red zone for a few minutes. It normally drops back down to 220 or so before I can get off the road to shut it down.

Would air in the coolant system cause symptoms like this? Any other ideas what it could be?

Thanks

 

[bromel]

Could be a lot of things. Is the radiator oem Mopar, or some store brand aftermarket? It makes a huge difference. I made the mistake of putting in an aftermarket radiator a few years go and it had trouble maintaining 210 in hot weather or beach driving. Finally put in a mopar radiator and it runs at 200 all the time.

Also, replace the radiator cap for good measure.

 

[ColoJeep]

How is it "overheating"? Is this condition based on the gage only?, or is it
boiling and forcing coolant through the overflow bottle?
A good Stant radiator cap and coolant change is a great place to start.
Welcome to the Forum!!

 

[TWiG01]

Occasionally you’ll end up with a bad (new) thermostat. Did you test it before install?

 

[TheBoogieman]

Clean the entire system with a quality chemical cleaner and use a Stant 195 thermostat. Then go from there.

 

[TJBart]

So I think I figured it out. I did a flush and it definitely needed it, and I went ahead and replaced the radiator cap just in case. The thermostat is a new 195F unit so I figured it was good. I also noticed the shroud was loose on one corner and re-attached that. And finally I noticed that the back of the radiator had a bunch of mud on the fins. I hit it with a garden hose and was amazed at how much mud came out of it. I just got back from a long run and it never got above 200F. I am thinking the mud in the radiator was probably the main issue. I washed it after I took it wheeling last weekend but I only sprayed the radiator for a few seconds.

Thanks for all the good advice.