Fan clutch bad?

First off i would like to say hello to everyone since this is my first post.

Well i have been having a over heating problem with my jeep now for a couple weeks or so. So i replaced the water pump and thermostat thinking it was the culprit but after that i am still having the problem. Ive been researching on here like every day to try and come up with why my rig is over heating. I really don't think its anything clogged because when i flushed the system everything was flowing great. Now ive been reading on how to check for a bad clutch but mine isnt showing really any symptoms of a bad one except when i heat it up or when it is cool i cant get the fan to turn but like maybe a quarter of a turn. Oh and i replaced all the dummy lights with actual gauges because of that and i got the info off of here thanks for that:cheers:

Under what conditons does it overheat? Idling in traffic? Freeway speeds?

At highway speeds it reads the line after 210 and when stopped it climbs above that. I really dont let it climb to much past that point with out cranking the heat on then it stays around that line.

MY Rule of thumb:

Overheating on freeway/hiway at speed - coolant flow problem - pump, radiator, heater core clogged.

When you flushed, did you flush the core independently. Like take the hoses off and run a hose top & bottom & back until it was all clear?

Overheating in town, city, idle, slo & go - air flow problem. Dirty, clogged or bent fins on rad, condenser OR a bad fan clutch.

yep i flushed the core both ways and it it had good flow going through it. It seems like there may be a coolant flow problem but when i flushed it everything was flowing great. Ive tried getting all the air out of the system but no way to tell for sure i suppose. Oh also the jeep is a 94 with a 98 motor in it so it has the open system.

So, your about down to the fan clutch?

Going to do a standard or upgrade to the more powerful ZJ HD fan clutch, NAPA 272310, $44?

Ill goto napa tomorrow and purchase the more powerful one. i just really hope thats the problem because ive been so confused about this thing and it has been driving me nuts trying to figure it out.

dduke454 said:

Ill goto napa tomorrow and purchase it. i just really hope thats the problem because ive been so confused about this thing and it has been driving me nuts trying to figure it out.

Click to expand...

A little schooling:

The thermal fan clutch works with a bi-metal spring at its front, a valve, and silicone fluid. When the fan clutch is not engaged, the fan will spin at 30 percent of the shaft's rotational speed. When engaged, a standard fan clutch will spin at 60-70 percent of shaft speed; the HD clutch will spin at 80-90 percent when engaged--it really moves the air.

Now, after sitting all night the silicone fluid will run out of the reservoir--this is normal. When you first start the engine all thermal fan clutches will engage for a short time until the silicone fluid is spun back into the reservoir.

When the air flow hitting the bi-metal spring is about 170 degrees (engine coolant will be about 30 degrees higher than that), the bi-metal spring will start to open the valve, the silicone fluid will start leaving the reservoir, and the fan clutch will begin to engage.

Now, what happens is as the fan clutch ages and begins too fail it will spin less effectively, resulting in higher running temps at idle and around town, you will usually be Ok on the highway just from higher air flow. Sometimes when you are sitting in traffic, and the temps start to rise, if you rev up the engine you might coax a little more effectiveness out of the old fan clutch and the temps will come down--a sure sign the fan clutch is past its prime.

Ok, hope I didn't bore you too much.

Good luck.

PS--don't let the counter monkey sell you a ZJ MAX COOL fan clutch--that won't fit at all.

yea i have read that before but i cant really see anything else causing the problem so i am going to replace the clutch. when i try to turn the fan it only moves as far as where the next blade is no matter if the jeep had been running for 15 minutes or hasnt been started in a while. I will get the same one as you posted the part number for.

I know this a very old thread, but I just wanted to add my experience here since I read this thread a week ago when diagnosing my overheating problem.

I only overheated on the highway, under load, like when I was going up a hill. I tried to troubleshoot the system based on what everyone said. My fan clutch "tested" out okay using all the tests you find on the internet. I finally gave up and took my Jeep to the local Jeep Guru to see if he could figure it out. He said that the fan clutch seemed to be working properly but it was "sweating" so he replaced it.

Apparently my fan clutch was leaking fluid and was not working properly at high speeds. This turned out to be the cause my problem.

http://www.naxja.org/forum/showthread.php?t=1141297

So in summary, you can be overheating on the highway only, not in town or at long stop lights, and still have a bad fan clutch.

Just adding my two cents to this:
I also replaced my apparently good working fan clutch,
and noticed an immediate stabilization of both highway
and stop-and-go temps. Now the temp gauge gets up to
normal and stays there under all conditions. So these
things do indeed wear out, as Mr Joe Peters says...
Good explanation of how they operate, by the way.

Slimer said:

So in summary, you can be overheating on the highway only, not in town or at long stop lights, and still have a bad fan clutch.

Click to expand...

Yes, I agree. Sometimes normal diagnosing doesn't solve the problem at hand. Good to look at it with fresh...and experienced eyes. Good to know.