Fan clutch

[94GMC2500]

Hello, if a fan clutch spins free when its cold does that mean its shot?

[trbankii]

Nope. It’s supposed to spin free when it is cold and engage when it is hot. Think about what it is trying to do and you’ll understand.

[JohnC]

Well, there's "freely" then there's "freely". There should be some resistance when it's cold. If you spin it by hand it shouldn't coast more than a half a turn or so. If it does, all the fluid has leaked out and it will not lock up when hot.

You can usually hear the fan roar for a few seconds on a cold start if you give it enough gas.

[94GMC2500]

Pretty sure its not locking up on a cold start. Is there a way to bench test a fan clutch? If I heat that spring with a heat gun until it moves should that lock up the clutch? Or does it have to be spinning fast for it to work?

[svcattle]

I would think the heat gun would work . Also a plugged radiator can keep em from working I had it happen if enough air can't get through the radiator to heat the spring they won't lock up

[arveetek]

If you've got the clutch out on the bench, bend the tab on the spring just a bit to force the system to engage sooner. I did that on my Tahoe, and it's made a world of difference. Now the fan actually kicks in and cools things down before reaching overheating temps. Before, it would hardly every engage until it was nearly too late.

Casey

[svcattle]

That's a good idea

[Robyn]

These cooling issues were a direct result of GM listening to "Whiners" that complained bitterly about the fan roaring when the weather was hot or the vehicle was pulling a grade.

Years ago I had a fella brought me a Suburban 4x4 that he claimed had a slipping tranny.

I pressure tested the thing and test drove the hell out of it and finally kept it over a weekend and took it on a family trip to the mountains.

Ran the dog doo doo out of it and the tranny performed awesome.

Things were fine.

The client came back a week later and was pissed off that the tranny was still slipping.

It was a hot day and we piled in the rig and headed up over the hill past the ranch here and whoa, the fan clutch kicked in and the client exclaimed, "seeeeeeeeeeeeeeeeeeeeee, the thing is slipping"

I'm laughing my A$$ off and he is just livid.

I explained that it is supposed to do that.

Opened the hood and let the thing sit at idle and heat up good.

Rev'ed it up and the fan roared and after a few moments it spooled down.

I said seeeeeeeeeeeeeeeeee, the roaring was there and the rig was not moving.

These complaints were rampant, and GM bumped the engagement temp up to stop the complaints.

After the advent of the plastic fans that are far quieter the issues have faded into the dustbin of history.

The big propellers that used to be standard issue were very noisy, but cooled well.

The 6.5 with perfect everything will not engage until the temp gauge hits 220 F if you are lucky.

The fan will pull a tad more air before the 220 F but does not really hook up good until (As mentioned) things are crispy.

AMAZING that a company like GM would listen to stupid complaints.

Spend a few pennies and put a sticker on the thing that says "THE FAN MAKES NOISE WHEN IT GETS HOT"

Fix a complaint and create a real problem

[svcattle]

I put a single 180 thermostat in my truck still have the stock fan clutch it runs 185 degrees cruising 70 mph highway it will go to 230 on long hard pull in 3 rd gear to the floor next summer I'll probly get the lower engage fan clutch or maybe I'll just bend the tab a little ? If she still running next summer

[Dvldog8793]

230...! IMHO that is deadly ground....
Even if it is only for short times, the oil temp is gonna be pretty high and it takes the oil much longer to cool down and you're pulling a load.
Might be a real problem some day....
When I pull a moderate load on a warm day my oil temp stays at about 200-210, on hard acceleration or a hill it gets up to 230. My coolant temps never get up past 200. Oil pressure is DIRECTLY related to the oil temp, even with 20W50 I notice a drop in oil pressure.
I wouldn't want to see what your oil temp is at 230 coolant temp.
IMHO, I would be careful and run a REAL good oil.

[svcattle]

I do not run it that hot but there is one pull that it will go that high for a just a minute . Lately I have not seen over 200 no matter what I do not use this truck to tow only pulled a trailer 3 times with it its my service truck and I have just about a ton of tools In it so it's loaded pretty good all the time . I was planning on doin the fan upgrade but I like the idea of bending the tab a lot better especialy on a thousand dollar truck that might blow up any moment

[94GMC2500]

I put a new Hayden 2840 fan clutch on mine. I can hear the fan roar with the hood open if I give the engine some rpm now. Never heard the fan before. That valve the spring turns was seized up on the old fan clutch.

[svcattle]

I put a new Hayden 2840 fan clutch on mine. I can hear the fan roar with the hood open if I give the engine some rpm now. Never heard the fan before. That valve the spring turns was seized up on the old fan clutch.

Is that the factory clutch

[94GMC2500]

Is that the factory clutch

Description said severe duty, engages at about 170 degrees. This is the late style threaded clutch.