92 Jeep Cherokee overheats at idle...

[stimac_911]

Hello,

I have a 92 Jeep Cherokee 4.0 that is overheating at idle (30-40 min). My wife is a mail carrier and when she drives mailbox to mailbox it overheats in 15 min. When I run the engine at 1,000 - 1,500 rpm I can overheat it in park in the same amount of time...

Work done:
New Radiator
New thermostat
New Temp Sensors x2
New radiator cap
2x Electric fans that do work
New water pump
New temp gauge (old one was off by 15 - 20 degrees)

I went to the dealership and they mentioned that the water pump may be in reverse (the pully turns couter clockwise). I took the radiator return hose off started the car and fluid came out. So, I do not think the water pump is running in reverse. I am out of ideas and the jeep; ofcourse, is worthless if it can not stay cool. Although it runs like a champ at 30 mph +. PLEASE help I and the mechanic are clueless on what is going on...

Thanks

Chris

[Saudade]

Did you flush out the block and heater core when you made the changes? Double check the routing on serpentine belt. Maybe the thermostat's in backwards. Make sure the radiator is full as well.

When the engine is hot, is the radiator and hoses hot as well? Does the heater blow out hot air?

[Ray H]

Originally Posted by stimac_911

Hello,

I have a 92 Jeep Cherokee 4.0 that is overheating at idle (30-40 min). My wife is a mail carrier and when she drives mailbox to mailbox it overheats in 15 min. When I run the engine at 1,000 - 1,500 rpm I can overheat it in park in the same amount of time...

Work done:
New Radiator
New thermostat
New Temp Sensors x2
New radiator cap
2x Electric fans that do work
New water pump
New temp gauge (old one was off by 15 - 20 degrees)

I went to the dealership and they mentioned that the water pump may be in reverse (the pully turns couter clockwise). I took the radiator return hose off started the car and fluid came out. So, I do not think the water pump is running in reverse. I am out of ideas and the jeep; ofcourse, is worthless if it can not stay cool. Although it runs like a champ at 30 mph +. PLEASE help I and the mechanic are clueless on what is going on...

Thanks

Chris

Sounds like its the mechanical fan viscus clutch. Im surprised that wasnt one of the first things that was checked. They are notorious for going/being bad. If the clutch isnt working as it should, the fan wont pull enough air. Even with a good fan clutch, XJs are marginal at best when it comes to cooling.
If it still overheats, tell her to put the air or defrost on when idling. I know that sounds backwards from what you should do. Heres the reason for it. The electric fan will kick on and off with the A/C compressor. That actually gives you better cooling than just the mechanical fan by itself.

[stimac_911]

Both electrical fans are bran new. They are definitely pushing air. Radiator has been flushed multiple times. The hoses are hot and I can feel fluided being pumped when engine is hot. One interesting note: at idle after the thermostate opens the top radiator hose (input) when sweezed only feels like a little radiator fluid is being pumped through is that normal? As the engine heats up more and more fuild starts to flow through the hose.

Also anyone know the direction the water pump is suppose to turn. AKA: Do the pump fins rotate in the direction of the scopes on the fins or opposite?

I was watching a show last night and something came to mind. What if since she is not traveling fast that all the hot air from the radiator is just building up in the engine compartment thus esculation the heat issue... Any ideas about this or how to correct it?

Thanks,

Chris

[Ray H]

Oops, I totally missed that it had an electric fan conversion.
If you had a fluid circulation problem, such as the pump being backwards, it would tend to show up while the engine is generating the most heat, ie: driving down the road. The fact that its fine driving but overheats sitting still indicates that its an air circulation problem.
Is her Jeep actually overheating or is the temp just getting "hot"? I mean does it boil over or just get to 220 or so? I know it seems hot but they are designed to run at 210. Ive done a ton of cooling system modifications to mine and it still goes to 220 while sitting on hot days. then the aux fan kicks on and cools it back down to 200 or so, then it goes through the cycle again.
Anyway, yes, the main problem with the XJs are that the engine compartment is small and sealed. That coupled with a smallish radiator and fans and youve got marginal cooling at best. There is no way for the hot air to escape from under the hood. The solution is to either put vents in the hood to let hot air out or to raise the rear of the hood by about an inch by adding spacers to the hinges.

[fredjacksonsan]

Originally Posted by stimac_911

One interesting note: at idle after the thermostat opens the top radiator hose (input) when sweezed only feels like a little radiator fluid is being pumped through is that normal? As the engine heats up more and more fuild starts to flow through the hose.

Maybe your thermostat is slow opening, or opens at a higher than normal temperature. You can test it by removing it and placing into a pan of water, then heating the water while checking with a thermometer.


Also, check out this guy's site, he replaced his hood to help with cooling:

http://www.go.jeep-xj.info/HowtoBonnet.htm

[fredjacksonsan]

Chris, I brought over your further comments from the other thread you started, no need to have 2 with the same problem.

Originally Posted by stimac_911

I own a 1992 Jeep Cherokee 4.0 that still overheats at idle. My wife uses it as her mail car and she can make it overheat quick (she doesn't even use the AC.) It runs like a champ when it drives down the road....

Work Done:
New Radiator
New Temp sensors x2
2 Electric fans ( 1 push 1 Pull 12 -10 Inches on either side of the radiator)
New Thermostat
New Gauge (Old gauge was off by 15 Degrees)
New water pump

When the car idles; even with the electric fans on, it slowly overheats... Everything has been repaced and even my mechanic is clueless. I went to the dealership and the only thing they could come up with is that the water pump is running in reverse (wronge water pump.. As a side note the pump runs counterclockswise from the serpitine belt). I took the return off the radiator started the car and fluid was pumping out... So I do not think it is in reverse. The car runs fine when it goes down the road. It takes around 30 - 40 minutes to overheat at idle. When my wife drives mailbox to mailbox(or low idle 1000 - 1500 RPM) it overheats in 15 - 20 minutes From Ambient air to 260 DEGREES. Please help this is becoming a useless pease of sh...

After reading that, I'm thinking:

1) Could the temp gauge be off?

2) Do you have shrouds on the fans? They make a huge difference

3) Is it boiling over into the reservoir or just showing 260* on the gauge?

[Saudade]

Check your belt routing

[mlp1911]

Have you tried starting/running it with the radiator cap off and letting it idle a few minutes to get the coolant flowing?

[fredjacksonsan]

Good point, a bubble in the system might cause the problem...but make sure the front end is about a foot higher than the rear to encourage any trapped air to exit the (open) radiator.

[stimac_911]

Wow thanks for all the responses. Stupid thing still overheats. After some investigation I belive that there is not enough air circulating through the engine compartment. Reason: My wife was delivering mail, she called and said it was alright at 220-230. I asked her to put th electric fans on. (Hard wired - a switch controls them.) Almost instantly the car jumped up to 250. (yes the fans are installed the right way.) So I think next I am going to raise the back of the hood and inch or so and see what it does.

Other notes:

Belt is correct...
Checked fluid with car raised in front - fine
radiator fluid does boil
Installed second temp gauge (1. so she can she while she is driving on the right side 2. The cars temp gauge was off +20 and yes car still overheats)

Question: How to do test the fan clutch. On the internet I found two ways:
1. Rotate the fan.... if working it should not rotate all the way around
2. When fan is on I placed a piece of cardboard in the way and the fan did not hesitate to knock it out of my fingers... (This is not a reccomended method...)

Anyothers?

Thanks again everyone....

Chris

[fredjacksonsan]

Hmm. Very odd. This may sound funny, but are the electric fans hooked up right? They should pull air through from the front and blow into the engine compartment. I thought of this after you said that once they were turned on, the temp shot up to 250*.

Also, check out this site:

http://www.go.jeep-xj.info/

The guy there did a hood replacement to make his Cherokee run cooler at low speeds. It may just be a matter of venting the hot air.

[RedneckXJ4x4]

did you ever try a coolant pressure test.. maybe you have a head gasket gettin bad?

[Ray H]

Im confused a little now. Do yuo have 2 electric fans or is one of them still the mechanical one?
I thought you said you had two electric fans at the top of the thread, now you are asking about testing a fan clutch.
Anyway, the viscus clutch should get noticably tighter or more resistant, to rotating when its hot than it is when its cold. You can check it by comparing how easy it spins when cold vs how easy it spins when hot. If you cant tell the difference, it may be time for another clutch. If you really want to fix it, there is also a way of drilling a hole in the clutch and inserting a screw in it that locks it so its always spinning at full engine RPMs all the time. You can also purchase a fan kit that eliminates the slutch and just runs the fan straight off the engine, both do the same thing. Im not sure of the details for either of these mods though. I havent bothered because mine stays in a reasonable range and they supposedly kill gas mileage because the engine is always pushing the fans, even above 35MPH, when the fans arent really of any use. Is your wife is usually driving slowly, these mods maybe something to consider to keep things cool.

[Stick89]

The water pump for the 2.5 and the 4.0 are identical except for 1 very critical
thing...one of them runs CCW the other runs CW.
They will bolt up and both use the same gasket but they rotate in different
directions
This is the 4.0


This is the 2.5


Notice the impellers??