Fan Clutch And Cooling Issues

SirDoopYJ

SirDoopYJ

YJ Enthusiast
Supporting Member
Joined
Oct 2, 2020
Messages
755
Location
Stick Red, Louisiana
I believe I need a new fan clutch. My Jeep starts heating up towards the red when idling at a red light or in traffic. When I start driving it cools back dowk to normal.

I tested the clutch and has resistance when hot. The fan stops immediatley after shutting off the a warm engine. This tells me my clutch should be good, but I feel I need to replace it anyways.

What are some decent brands. I saw Hayden should be good, but I only see a heavy duty. I would rather a standard. I don't want it to be loud.
 
That does sound like a fan clutch problem based on the symptoms, though it’s puzzling why you’re feeling resistance still. Who knows, can’t hurt to change the clutch just in case.

I run the Hayden heavy duty on mine. It was practically identical to stock, all of the factory 4.0’s came with “heavy duty cooling”, and I have half a mind to believe Hayden supplied them with their fan clutches. I don’t know that for certain but they looked the same.

Anyways, my Hayden HD is loud but stock was very loud as well. They’re practically the same to my ears. Some people in the TJ world run the one for the 2.5 on their 4.0 and claim it’s much quieter and still doesn’t overheat. It is known as a standard duty. Maybe that’s worth a try for you. The noise of the HD doesn’t bother me so that’s what I’m sticking to.
 
Possibly. When I first got into Jeeps I just thought the engine was loud and made tons of noise. Had no clue that it was the fan making pretty much all of the noise.

Do you hear the sound of a hurricane when you start it up? Or when you rev it out? That is the fan noise specifically.
 
I once put a heavy duty fan clutch on my J20 and I could feel it kick in on a 360 V8.
And, yeah, it was noisy! But it worked.
Can't really weigh in on the YJ clutch, mine went away long ago in favor of an electric fan.
 
It doesn't really spin when it is cool either. If I really force it, it does about a full spin and maybe a quarter.

Maybe it is at the beginning of failing? I haven't checked for any leaks in it.

What is funny, is that it gets close to overheating when I am out and about. The moment I bring it home or have it on at home, it never overheats.
 
I'll throw out another thought here. yes, it sounds like your clutch is working correctly but for $40 or so its worth the piece of mind down the road. Far as noise goes IIRC once moving about 30 mph or so the fan does little to nothing as the speed of the air does the job. At low speeds the clutch kicks in and dependent on HDuty or even who made it the fan spins at X percent of full lock up. I'll say on my 91 I never hear the fan, but testing like you have done shows it fine and it never overheats.That being said After looking back on your "new to me" jeep thread and the pics of the radiator I thought looked a bit plugged up internally even after the flushes. Looks can be deceiving and you cant see down into the center of the core. I recall you going thru the hassles with thermostat replacements and low temps. Like Macho and the guys indicated they need the 195 thermo to run correctly and go into closed loop ops. My 91 runs typically at 210ish or just past the 12 position when under load. Idling it runs about 1/8" under that mark 195ish Id guess. Just to double check your work make sure the coolant is a 50/50 mix. Ive heard of guys running 100% coolant thinking more is better, thats not the case. Ive also seen personally where a water pump impeller corroded away to the point of doing little to nothing. Cant recall if you replaced yours but if all else fails thats a possibility.
 
Yea, I don't mind spending the money for a new clutch.

When I bought my Jeep, the first thing it needed was a new gauge. I bought a Crown brand. It would get to 210 pretty quick no problem, a few minutes or so. I would feel my feet start to get hot from the firewall and the hood would be extremely hot to touch. I had the overheating at idle problem then too. This was when I started taking everything apart to do the flush and change to a 180 termostat.

For coolant, I use the green stuff from Autozone with distilled water. I pour out both into a bigger separate container so that I know for sure I have a 50/50 mix. I have read that 100% coolant is not good for the motor.

I have changed out the temperature sending unit, which seems to give me a more accurate vs the old one. The old one would have the gauge show about 110 all the time when I changed to the 180 thermostat, which didn't make any sense. The new one shows the gauge close to 180 unless I hit a red light or idle for a long time, it will start to over heat and then drop down to a little under 210 and stay close to 210 for the remainder of my drive.

When I pulled the radiator out I wanted to replace it, but a few people on WranglerYJ sub reddit told me to keep using it.

I plan on putting the 195 back in. Idk about the water pump being an issue. The only thing I have changed cooling wise is the gauge, sending unit (the one near the firewall), coolant, thermostat, and switched to the screwdriver adjustable hose clamps. The PO told me he had changed out the coolant sensor that sits on the thermostat housing.
 
I went with the Hayden HD. It took me about an hour to change it out. So far no over heating issues while idle. The hottest my motor got was near the first small tick past 210 when idle. So about 220 230? Idk how this gauge is divided up.

Motor would cool back down to about 180 when moving. I also didn't notice a sound difference.
 
Your Jeep is weird. Mine never goes past 210, idling or anything. It doesn’t dip on the highway either. It’s basically always just barely to the left of the 210 line.

I’m surprised you’re still seeing roughly 40-50° fluctuations between highway or idling. Doesn’t make sense to me with a new fan clutch unless something else like the water pump or something is flowing more at higher rpm. I don’t know that you necessarily have a problem, but I am curious what is causing it to act the way it is.
 
This is sounding like a sick radiator or the wrong radiator, dunno if there's a difference from a 4 to 6.
Mine goes to the first mark under 210 and stays there, granted I have an entirely New cooling system.
 
jeepjoe43 said:
This is sounding like a sick radiator or the wrong radiator, dunno if there's a difference from a 4 to 6.
Mine goes to the first mark under 210 and stays there, granted I have an entirely New cooling system.
Click to expand...
No difference between 4 to 6, they use the same, but agreed something still doesn’t seem right for sure.
 
Maybe it is the 180 thermostat or maybe something happened when I pulled light wire harness, grill, and driver fender off. Ever since then my gauge would sit that low. Idk. I will investigate more this weekend.
 
SirDoopYJ said:
Maybe it is the 180 thermostat or maybe something happened when I pulled light wire harness, grill, and driver fender off. Ever since then my gauge would sit that low. Idk. I will investigate more this weekend.
Click to expand...
Shouldn't be related to the light harness although I guess stranger things have happened. The light harness is literally just controls of the lights and the windshield sprayers. the grounds in that harness attach to the grille but again, only for the lighting circuit so if those were messed up you'd just get sporadic or fully non working lights up front, and no sprayer action.

I'd say the 195 is definitely worth changing, it'll keep you at least at 195 degrees at a minimum which is good, although yeah maybe the radiator or water pump needs some attention.

Something a lot of old Jeep owners do is they buy a jeep and immediately throw a whole new cooling system at it. Radiator, water pump, fan clutch, tstat, radiator cap, and flush the fluid. Don't know if that's a waste of money or not but it sure is hard to truly overheat when everything is new.

Of course, we still aren't 100% sure your gauge and sender are even representing the numbers properly. Although they probably are, and it is probably representing actual fluctuating temps in the system.
 
Like the guys say something isnt right still. An option is to pick up a harbor freight infared gun and shoot the temps at the thermo housing as the temp gauge fluctuates. A few random thoughts for the guys to ponder. #1. at speed your trans in not locking up the converter causing it to run so hot. #2 You should have a reverse rotation w pump. Is it possible the wrong pump was installed by the PO? Pumps will move water running the wrong direction, just nowhere near as well as the correct direction their made for.
 
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Changed the thermostat back to 195F and redid the coolant. My temps are at 210F or a little higher. My fancy multimeter reads my motor at 220F near the sending unit on the back of the head, so the gauge seems accurate. There were a couple of times where my gauge was reading higher, but by the time I could pull my Jeep over to check it, it would cool back down to 210/220F.

I either need to allow it to burp more, or go ahead and change out my whole cooling system.
 
Sounds like your making headway. keep an eve on the coolant recovery bottle. If the cap is good the system should purge the bits of air out and as it heats and cools it will purge out any bits of air and pull in coolant to void the radiator of any air. Personally Id still consider a new radiator for piece of mind.
 
What are some trusted brands for a radiator? I think I recall reading that the factory are a copper core, but all the new ones are an aluminum core. Does this make a difference?
 
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