Fan clutch use and advice.

Maybe this should be in the stupid questions thread. But im nut sure. Jut lookng for some peace of mind.



My fan clutch comes on a soon as you take off after starting and howls like crazy. It goes away after a minute or two. if I'm using my ac it will howl after every stop sometimes, then go away as usual. I understand the ac needs that. I get that this is what its supposed to do to keep the engine/ac cool, and pretty much every truck has done it and its normal. But it seems to be robbing allloooot of my horsepower and makes the engine struggle big time. My confusion is why is it running so much when my temps are beyond good? I know some clutches are adjustable. I wouldn't mess with that, unless I had advise from may people because i know the risks, but could this be adjusted just a hair so i wouldn't sound like a train so much and have extra load on the engine? Or would the increase in engine temps be allot worse rather then leaving it alone.This is almost a 4 or 6 month new fan clutch. I do have my fan cover and collector on. I am aware how a viscose fan clutch works.

(some more info) I live in the +100 degree heat. Long story short I was running a little hot, plus big rising temps then right after big drops. I did flushes and everything with little results, I even washed out the radiator and condenser fins with cleaner and mild pressure water. Turns out all along it was just a bad thermostat...I felt dumb as all heck. Now that I did all that and changed it, my engine runs at pretty much the exact 1/5th mark normally, and on a 110 day its just a hair over. ( im not to keen on what exactly that temp that is) But I know it runs cooler now then iv ever seen it in my life. I can use my cod reader to give you the exact numbers if you're curious


Is this completely normal or weird?
Does the fan cool the physical engine past the radiator?

My fan roars when I first start up, and take off, and I don't notice it after that. I'm in a much cooler area than you, Though. It's supposed to reach 95F this week, and that will be VERY hot for this area. Also my AC doesn't work. I'm guessing the behavior your seeing is normal for your climate. I've never heard of a fan clutch being adjustable.... maybe that's a newer thing, as I believe some are electronically contolled, even if mechanically driven.

You'll get some cooling by the air rushing past the engine, but the vast majoirty will be done by the coolant circulation.

Pretty common, my fan clutch sounds like a jet for about 2 mins when first started up then it's fine.

I swapped my 5-blade metal-bladed fan for a composite 11-blade S-10 fan. '97+ 400's & '99-'02 800's got 'em too. They fit the TBI trucks.
Same size. 19'' diameter. Quieter. More efficient.
$5.00 at the wreckers. Make sure to check those for split blades & cracks close to the hub.
Dorman makes that fan as a direct replacement. In white.
The S-10 fan is 1/2 the price of the one for a 400. Same fan! Bolts-on.
Dorman S-10 part number 620-602. Last I checked, that was around $40.00 with no clutch. The Dorman 11-blade for 400's & up was in the $85.00 range.
GM also sells the 11 blade composite fan, but in black.
...and probably for a lot more than the Dorman part.

sewlow said:

I swapped my 5-blade metal-bladed fan for a composite 11-blade S-10 fan. '97+ 400's & '99-'02 800's got 'em too. The fit the TBI trucks.
Same size. 19'' diameter. Quieter. More efficient.
$5.00 at the wreckers. Make sure to check those for split blades & cracks close to the hub.
Dorman makes that fan as a direct replacement. In white.
The S-10 fan is 1/2 the price of the one for a 400. Same fan! Bolts-on.
Dorman S-10 part number 620-602. Last I checked, that was around $40.00 with no clutch. The Dorman 11-blade for 400's & up was in the $85.00 range.
GM also sells the 11 blade composite fan, but in black.
...and probably for a lot more than the Dorman part.

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I just swapped an 11 bladed Motorcraft fan onto my 383 in my 97 Express. I had to slightly open up the bolt holes with a step drill because the Ford clutch uses smaller 8mm bolts. That being said ran it on the dyno yesterday. It was 102°F in the shop. It ran continuously for 5 hours with the a/c cranked up. I made nearly 30 pulls in those 5 hours adjusting fueling and timing. The engine never got over 185°F. I did have a pretty good size fan pointed at the grille to help with cooling but I have seen other vehicles like Vettes and Camaros boil the coolant they get so hot in similar conditions. Motorcraft part number YA-249.

Here's the fan you want

WHAT VEHICLE??? WHAT FAN CLUTCH???

chriscg said:

My fan clutch comes on a soon as you take off after starting and howls like crazy.

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Common at first start-up. Should quiet down fairly quickly.

chriscg said:

It goes away after a minute or two.

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I'd expect it to quiet down after less than one minute.

chriscg said:

if I'm using my ac it will howl after every stop sometimes, then go away as usual. I understand the ac needs that. I get that this is what its supposed to do to keep the engine/ac cool, and pretty much every truck has done it and its normal.

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Depending on temperature, humidity, etc...could be totally normal.

chriscg said:

But it seems to be robbing allloooot of my horsepower and makes the engine struggle big time.

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First Guess: You have problems with the engine that are not related to the fan/fan clutch.

chriscg said:

My confusion is why is it running so much when my temps are beyond good?

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How do you know your temps are "beyond good"? The dash gauges are notoriously inaccurate.

chriscg said:

I know some clutches are adjustable. I wouldn't mess with that, unless I had advise from may people because i know the risks, but could this be adjusted just a hair so i wouldn't sound like a train so much and have extra load on the engine? Or would the increase in engine temps be allot worse rather then leaving it alone.This is almost a 4 or 6 month new fan clutch.

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They're adjustable, but in fairly large steps. You don't adjust them "a hair".

And kiss any new-part warranty good-bye if you tamper with it.

chriscg said:

I do have my fan cover and collector on.

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I have NO idea what a "fan cover and collector" are.

Never discourage someone from trying to learn something.
Knowing nothing is closer to truth than a mind filled with falsehoods & mis-information. Knowledge is power. The way to acquire knowledge is to keep reading.
Wisdom comes from observing.
We're all born ignorant, but one must work hard to remain stupid.
No-one here is stupid.
Except for that one guy that wanted to pinch his rear brake lines off with some vice-grips, justifying his actions with "...it's just to go back & forth to work for a week or so until I can afford to do a brake job."
Now that was stupid!
...and I told him so, too. In no uncertain terms.
'Tempted' was stupid. Blatantly! (The O.G. guys will concur on that one!)
Kudos to you for being humble enough to realize your limitations & reaching out for help. ...for information. ...for knowledge.
If we could still hand out 'rep' points, I'd throw a bunch your way! Just because.

Condolences on your Dad's passing.

Sounds pretty normal to me.

You could possibly get a part number off of it and see if it's the "severe duty" version. If it is, you could swap it for the standard version. I have one of those severe duty ones on my LX and it's definitely a power robber.

The silicone fluid in the "clutch" can be dialed in to a level of "grab". When I had my 80 series Land Cruiser a popular mod was to replace the fluid in the clutch with RC car differential fluid (silicone) because it had better "grab" and helped low speed cooling. Basically, DIY severe duty clutch.

Has anybody tried this Flex-a-lite fan?