My Daughter cam home last night freaking out because the Jeep was smoking and the temp gauge was high. I took a look at it tonight and replaced the thermostat just because it was only $7 and a 10 minute job. No luck, still hot. It doesn't appear to be leaking/weeping out of the water pump at all so I am suspicious of the radiator. I had to have it flushed a couple times this summer because of the thick, brown sludge that kept coming out so maybe she's clogged? Is there a test I can perform to see which it might be?

Changing the crank position sensor was bad enough and changing the water pump and/or radiator doesn't look like a treat either.

 

Neither is very hard to change,but to check the pump,let it get warm enough to open the tstat and then squeeze the upper hose enough to allow you to feel if the pump is working,like a water hos e. Check the inlet to your a/c cond in front of the radiator and see if it is plugged with bugs and debris. Is your electric fan coming on?

 

lots of things to check for this... do a search on cooling. I just did a complete overhaul of my 1990's cooling system (closed system)... so hopefully I have a couple of suggestions to check.

1. Flush the radiator. If there's a ton of brown gunk coming out, you might be clogged, like you thought.
2. Is the alt fan coming on? This is the AC fan, but it also is supposed to kick on at about 220* to blow more air over the engine. If it's not coming on, check the power and make sure it's getting power, and if so, maybe replace the coolant sending unit.
3. Have you replaced the fan clutch? That can be a biggie, if the fan clutch is going out, you won't be blowing enough air ,esp. when idling. (is it only getting hot when idling, or is it running hot all the time?)
4. When the engine is at temperature, can you feel fluid moving in the hoses? Feel the lower hose (careful of the electric fan) and see if it's collapsing. Mine didn't do that, but I've heard that it can happen and can impede coolant flow to the rad.
5. To my experience, the water pump works or it doesn't (at least that's my experience). Mine blew with no warning driving luckily on a city street... blew water all over, steamed up a lot. No damage, thankfully, but a pain.

Just some things to think about. There are a lot of guys here much better at this stuff than I am, but these are the things I dealt with recently so hopefully it helps and gives you a starting point to troubleshoot from.

KK

EDIT: And I've always found that the manufacturer's thermostat seems to work better than aftermarket, and it's only about a $12 part... sometimes it's worth it (and just as cheap) to get the parts directly from the dealer.

 

I don't feel a thing when squeezing the hose which I know isn't good. The electric fan doesn't come on either... Can everything blow at once! **Edit, I need to go let it get above 220 to make sure the electric fan is/isn't working.

 

I think you have a few issues,if you do not feel water flow, was it up to temp?is your a/c charged,this will also prevent your electric fan from coming on,start your jeep and put on the a/c,your electric fan should come on,if it does your sending unit on the tstat housing is proabably bad. The other thing is if your pump is not working your switch may not see enough water temp to activate.

 

Is it possible for an entire radiator to be clogged? About 4 months a go I had Lube Pros flush the radiator and I didn't think they did a good job so just 3 weeks a go I had it "super" flushed and finally the coolant was green again. I am going out to get it hot and check a couple things..

 

It is not liley that your entire radiator is plugged,but it could be plugged enough to cause overheating.

 

Just back back from driving around. After a minute or so the temp shot up to about 220 or so and then all the sudden dropped to 180 or so. I turned on the AC and continued driving and it never got past 180-190. I parked and let it idle for a bit and it crept back up to 210-215. The I drove it some more and it cooled down on the road. When I stopped again and let it idle, it crept up to 220-225 but the electric fan never kicked in and the hose was as hard as a rock. I thought she was going to blow! After a bit more driving and idling, it got really hot 250+ so I parked it and the hose sprung a pinhole leak and now it is in the driveway cooling off for the night. Can that sensor on the thermostat housing cause such problems? The thermostat itself is completely mechanical right. I'm not a cooling guy so I can't figure out why it's not circulating.

**What would I accomplish by taking out the thermostat and driving it for a bit?

 

Yes it can,if you turn on your ac and the fan comes on then the a/c side is ok,the sensor sounds like the problem,the electric fan is primarily for the a/c,but it is suppose to come on when temp reaches 220.
If it is heating up and cooling down when you drive,I would say your water pump is ok,star t with the switch.

 

If the aux fan didn't come on, see if it comes on when you engage the AC. If it does, replace the coolant temp sensing unit, that should fix that.

You're getting hot when idling... again, I'd suggest checking your fan clutch. Those things need to be replaced every so often and often go overlooked, but can help a lot with idling temperature control.

And some might disagree, but I'd say not to remove the thermostat... Jeeps want to run at about 210*, and they run best there. If you run it too cool, your gas mileage will suffer as a result.

 

The switch is to start the fan at 220,pulling the tstat will not prevent it from overheating,best to leave it in,it sounds like the switch is the problem.

 

The AC fan will not come on no matter what. I got it up to over 220 with the AC on and still no electric fan.

I am a bit confused about the switch/sensor. I was talking about the thermostat sensor in the housing, but I reckon their is an actual switch for the electric fan?

Whats the best way to check the fan clutch?

I really appreciate the help also. This Jeep has been flawless thus far so this is new to me.

 

On yours that switch is for the electric fan,so if it is bad the fan will not start. The main reason for the fan is for the a/c,the things that will cause the elctric fan to not come on are,the switch on the tstat housing,a/c low on freon,the fan itself is bad. I have always just looked at the mechanical fan,if it appears to be spinning good I do not worry about it,there is proabably a more technical way.

 

I failed to mention that there are relays on the fan that can go bad also,it sounds like the switch.

 

ok... if your jeep is cooling down whie driving and over heating when sittin still... its for sure the fan... when diving air is blowing through the radiator and cooling the system... when sitting the fan is suppose to do this... i would start by unplugging the fan if its electric and checking to make sure it has power at all when heated or AC's on... if no power then you can go up the chain to find out why... if there is power then your fan is burnt up... if no power from either the AC or th sensor then i doubt they would both go out at the same time...check your ground... the ground from the fan would cause both not to work since they share the same wire... you could also apply ground and power to the fan to make sure it works... you AC being on is not designed to keep you jeep cool... so if neither work theres probly 2 problems unless its that ground... did the AC work before and not now? if so then your AC and overheating happened at the same time which leads me back to believe its the ground wire... if you have a mechanical clutch fan then its gots to be replaced... but i dont think you do