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Possible Fan Clutch Issues On A Duramax?

ColoradoSkiCountry

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ColoradoSkiCountry Senior Enthusiast

ColoradoSkiCountry

Posted
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Hey All,

 

I have a problem where sometimes in the morning after I have started the truck (and usually let it idle for about a min) I will take off and notice that the fan clutch is engaged. It will generally stay engaged for as little as 30 seconds and as long as 2-3 minutes. I notice that if I do a hard acceleration it will disengage much quicker, otherwise it lingers on. Is this normal? It does not happen all the time, and it only occurs in the morning. The AC is not running, and the truck never seems to require the fan clutch to be engaged fully while I am driving during hot summer days. Temp always seems to stay where it should.

 

Thanks

jro909 Senior Enthusiast

jro909

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is it humid or damp in the morning where you live? mine will kick on in the morning if its really wet or humind but it won't last past shifting from first gear...are you sure its the clutch fan or could it be the turbos?

Bluedog Enthusiast

Bluedog

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Definitely not the turbo. It is the fan clutch. Not humid here, Colorado rarely gets above 35% humidity. Thanks for the info Shane! If it does it on an 05 then I guess I am safe on an 08

 

Not so much with the humidity, I notice it more if the truck has been sitting for a while (week) and especially if it is a little cool out. Nothing to worry about - they all do it when the conditions are "right" and the fluid has accumulated in the clutch. Just annoying when you are trying to sneak out of the house at 4 am...

Shaners Senior Enthusiast

Shaners

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I sound like an airplane taking off at 5:30 in the morning in a quiet neighborhood! It only does it sometimes (prob less than more). And it will usually quits after one block or may go several blocks. It's seems pretty random.

 

I had a 1988 S-10 4.3L that did it every morning no matter what!

Shawn T Enthusiast

Shawn T

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This is definitely normal behavior. Every duramax I have ever been in has done this. It is characteristic of the type of fan clutch it has.

 

Ditto, it must have to do with the fluid in the clutch itself. It seems to "lock up" when setting in cooler weather and as soon as the engine compartment starts to warm/and the motion of the fan spinning it releases. Every Duramax I have owned has done this including my 99 5.3L 1500 gas.

Diesail Enthusiast

Diesail

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Has has to do with viscous coupling that engages the fan. Depending on tempature when it was stopped it may take a few minutes to warm and release.

 

Funny story, I got pulled over by a cop who had another car pulled over in a 25. Truck was in first gear, high rpm and fun engaged. Even thought I was going slow and nowhere close to him, it was loud enough he that I was going to run him down. After a good arse chewing he let me go.

Rat4go Enthusiast

Rat4go

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Back in the day (early 90's S-10 pickup!), I asked the dealer service writer about it and he called in 'morning sickness' and said it was normal. I did some research on it back then because most service folks wouldn't know their arse from a hole in the ground and found that:

1) Service guy was correct....it's normal.

2) Like others have said, it's a 'viscous clutch' thing and is a function of the temp you shut off at and how long it sits and how cold it gets while it's sitting.

3) My '03 Dmax does it, but no where near as bad as my 91 S10 was as it 'pumps out' in a much shorter time at much lower RPM in the Dmax.

4) It sort of lets you know that the fan clutch still works!

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