If the aux fan DOES run when you have the AC or defrost on, but isn't kicking in when temp hits 220*-ish, it's likely that you'll want to replace the coolant temperature sending switch... it's on the driver's side of the radiator, bolts into the radiator and then onto an electrical switch that engages your aux fan at the appropriate temperature.

 

The fan is easy to check. Just turn on the jeep and let it run. Pop the hood and watch it. The fan should come one when the temp hits around 190-210, if not sooner. If it keeps climbing and the fan isn't coming on then you have a fan problem. After reading the original post though it definitely sounds more like air in your system. Have you checked the oil lately to make sure you aren't getting any water in it? Hopefully your heads not cracked.

 

Not necessarily. The fan can work but the relay could be out or the temp sending unit can be bad. Sounds like the fan does engage, just not automatically at temperature.

 

Bingo! The soft hose collapses under vacuum when the stat opens and restricts coolant flow.
You can test this:
1. First just squeeze the hose, if you can't feel the spring inside that is most likely your problem.
2. You can feel the lower hose while your warming up... Around 190 degrees you should feel it start to gradually collapse as the stat slowly opens. You would be able to visually see this as well. If it doesn't collapse then it's most likely not that...
Chances are it is though if there is not cable inside the hose!
Mike

 

Sweet,
i was hoping someone would agree with me and i would feel just a little smart. i will go out there in a bit to check that out. i am thinking that right around the 220 mark the hose collapses and restricts the flow causing the temp to suddenly spike. i have also called around and found that only the jeep dealership sells the hose with the spring in it around here. so most likely a lot of people are putting in the wrong hose.
hopefully this fixes it and maybe can help out a lot more xj's overheating.

 

I can't remember which of the 2 hoses coming from the radiator are supposed to have the metal windings inside them, that don't allow the hose to collapse. I don't have my Cherokee with me at this time, maybe somone else can check theirs and post. If he put a super cheap hose on it without the inner metal winding it may be collapsing when the thermostat opens and not allowing the coolant to flow. Squeeze the 2 large hoses and see if they are ridgid... Sorry, I just can't remember if 1 or both are supposed to be... Someone else will help us on that.
Mike

Well I told you this in the other post last week!!! Thought you had checked it!
Mike

 

i had checked to top hose but didnt really know how firm the spring hose should feel. someone told me earlier that it was the lower hose that is suppose to have the spring in the hose.
i seriously hope this is the case

 

I told you to squeeze both hoses, that one of them has the sopring in it but I couldn't remember which one. So you took the advice and only squeezed the top one? I wasted a lot of typing and thought time on this. You have to do your part!
People that post here looking for the silver bullet solution without doing any testing are frustrating! Next time there is a problem let me know I will drive to your house and think for you!
MIKE

 

mike your the man ! i would have never thought of that one .. the hose and deff a good burping .i would say would be the cure ..that is if the fan is kicking on when its soposed too ..

 

When you write in seeking advice and get good knowledge in return, you should take advantage of it. Many on here have experienced overheating problems and some have never solved them. They damage or sell their Jeeps in disgust instead.
Follow the good advice given, and start enjoying your Jeep the way you intended to when you bought it.
Dan

 

Dan .... do you mind if I put this in my signature ?


I'm noticing this more and more lately on all the sites I go to ... it's almost enough to chase me to Pirate.



Joe

 

I have taken every bit of advice that everyone has given me that my time and pocketbook would support so far. i am also trying to gain knowledge about jeeps to maybe help someone out in the future. i checked both hoses and also ran the engine with the caps of and the heater on at 1500 to 2000 rpms. nothing. and when i get more time i will do a full flush. the temp switch is on order and when that comes in i will change that. so i have taken everyones advice. the only reason i update this thread is to keep everyone else updated. maybe it will help someone else.
i have used the search option and when i type in overheat, none of them sounded like the issue i was having. Just remember we all were new to jeeps once.

no disrespect intended at all towards anyone

 

Sometimes when seeking advice,the hardest thing to do is keep your ears (in this case eyes) open and listen (read).

 

i thought i had, maybe i missed something. i am not the type person to ask for advice then not listen. i guess something i wrote earlier sounded diffrent then i it did on the key board

 

i was looking over everything today when it was around 220 or so without the a/c on and noticed the fan was not turning very fast. i mean i stopped it with my finger, hurt a little bit but it stopped fairly easy. later after changing my temp sending unit it was spinning more than twice as fast with the heater on (when i was trying to get all the air out) .

Is the fan designed to run at diffrent speeds?