So a few weeks ago I was on my way to work and I look down and my Jeep was in the red zone for the temp gauge, so I killed it and pulled over immediately and had it towed back to my house. Previously to that I had noticed that it had been running a little warmer than it normally would, and at some points it got to almost the 3/4 point on the gauge, but that was only once or twice. So that was my situation, when the jeep overheated, it puked all the radiator fluid on the floor, and the fluid didn't look very good, it was pretty rusty looking. So over the past couple of weeks, I have been overhauling all of it. After flushing everything as well as I could, I put in a new radiator, new radiator hoses, some other coolant hoses that go back to the heater core area, and I also changed the thermostat. Today I took the thermostat back out because I realized that the thermostat was installed wrong, (I read that the air bleeding valve thing should go up) and so I took it back apart and installed it correctly, or at least what I believe is correct. So I filled it up and fired it up, and sure enough it went right past normal operating temp and straight into higher temps, so I killed it. Now I am stuck, I don't know what else it could be, any help would be greatly appreciated, I'm not super knowledgeable about all of this coolant system stuff, but I have done lots of other work on all other things. Does anybody have any ideas as to what could be going wrong? I could really use some help, it is just a 95 Jeep Cherokee with the 4.0. Thank you in advance for any help you can give!

Side note, I just realized that the thermostat housing is completely sealed up, it did leak a few drops, could this cause the overheating problem? I will definitely fix it either way, I just need to go buy a new gasket. It doesn't seem like that could cause it to overheat, but then again I don't know much

 

Did you replace the waterpump as well? This is what circulates the fluid through the sysytem. The fans inside of it, have a tendency to rust away after time. Any leakage of fluid on the passenger floor? That could be a sign of a bad heater core. You could also have a bad sensor on the thermostat. Have you verified the temperature with a laser thermometer? Shoot it right at the thermostat housing and it will give you an accurate reading.

 

Alright man, thanks for the tip. I changed the water pump out this afternoon, haven't tested it yet because I need more coolant. And can you explain the thermostat sensor? I do have a laser thermometer I can check stuff with, where would I check? And could that be the problem, because my gauge appear to be working just fine. What is that sensor used for? Thanks for the help!

Edit: okay I see you said where to measure temp. So anywhere right on that thermostat housing will do? Thanks

 

I would shoot it right at the housing where the sensor is housed. The sensor should be on the right hand side if I remember correctly.

The sensor can appear to be good, but still fault out once the temperature starts rising.

Are 100% that you have all the bubbles out of the system? You should be blessed to feel all the houses getting hot. If not, you have a bubble or a clog somewhere. Also, what thermostat did you buy? May be a bad one out of the box. That has happened to me twice now.

 

Very likely a bad head gasket.

You don't have to verify temps. It boils over. It is hot.

 

Thanks to everyone who helped, turns out the water pump did the trick. I'm not sure why though, because the old one didn't even look that bad, just light surface rust. But hey, I'm happy the jeep is back up and going again. Thanks again guys!

 

Glad to hear you're back up and running! Keep an eye on it though.

 

Alright silentj, the jeep has been running well, but one thing I am noticing is it still gets hot after I cruise down the road, and come to a stop the temp will go past the 210 mark and halfway to the next mark, and then it will get control and quickly come back to right under 210, but still touching that mark. And then I pulled into my neighborhood and parked and it was sitting almost at that next mark. I then turned it off. I know that it shouldn't do that, but I also don't know what to do next. Sorry to be a bother, but this is my first vehicle and I have learned a lot with it, but I clearly still have to learn a lot more.

Note: When this happened I had driven about 15 miles on a 109 degree day, with the a/c on full blast. So I do understand that this is stressful to the system, but it should be able to handle that right? I have had it for a little over 2 years now, and last summer it seemed to do just fine and always stay at that 210 mark. Thank you

 

Hmmmmm. Sitting at 210 or just beyond that mark is normal. Mine does that frequently when the A/C is on. A few more questions for you... do you have both fans shroud installed? Is the A/C fan working (the one on the passenger side)? It should engaged with the A/C. When was the fan clutch replaced for that fan?

 

The electric fan for sure works, I can hear it kick on with the A/C. The electric fan has all its plastic attached to it, and the mechanical fan shroud is in. And the clutch for which fan? I have never replaced a clutch for a fan, but the mechanical fans starts up with engine and everything, and the electric fan just comes on with the A/C or when it is really hot I think. And going down the highway it was doing great, it was just when I got home and parked that it almost touched that line after 210. That sensor on the thermostat housing was mentioned earlier too, should I still replace that?

 

If and when it hits 240* +: That's when to start worrying.

Pay no mind to minor fluctuations. Rising temps on shutdown is normal and is to be expected.

 

Okay, I will keep an eye on it and make sure nothing too wild happens. Thanks you guys for all the help

 

Sorry to bring up an old thread, but I figured I would give an update on the jeep after a few weeks of driving. The new parts seem to be working great and I have had no leaks at all (Knock on wood). The temp still fluctuates a little bit on heavy traffic and such, but it is definetely doing good. Thank you to all for the assistance. Im going on a 165 mile trip soon, over the grapevine in So Cal, so Im really hoping that my jeep will make it otherwise Im gonna have a bad day. But its been doing great lately and as long as traffic isnt bad i feel pretty confident.

For anyone that may be in a similar spot as I was a few weeks ago, I would say go ahead and replace the water pump. My water pump never leaked through the little hole to notify me that it was going bad, and even with the old one taken out it didn't look that bad, but the new one did the trick and got coolant flowing again! It really wasnt that hard to do either, just remove the fan shroud and the electric fan, then remove the pulley. The pulley was a pain, but once you get past that it was super easy. Oh, I guess you need to take the serpentine belt off to, but that was easy as well. Plus the water pump was like 40 bucks and came with a gasket, and that includes tax. Pretty sure you can get a cheaper ont too. All in all a pretty easy job. And to anyone that may be in a similar spot I was, good luck!

 

Thanks for the follow up.