Engine/Transmission (1998.5 - 2002) How to check fan clutch?

[hammersley]

Ok - how can I check my fanclutch? If I need a new one - where (other than dealer) can I get one?

 

[ProspectorTim]

If you open the hood and watch the fan when you shutdown the engine, when the engine is cold, the fan will free-wheel for a few seconds. When the engine is hot, the fan will stop immediatly - and is more likely to cause the belt "chirp" from the sudden stop.

 

[rblomquist]

I've been wondering the same thing in regard to where you can get one other than the dealer

 

[hammersley]

I thought the Chirp was

on the main crank as the engine stops Right Now and the belt continues to turn causing the chirp. I don't think it's at the fan pulley.

 

[MCummings]

Another way,, when the motor is hot ~190*F turn the truck off, open the hood, and see if the fan turns with much resistance. If it's hard to turn, then it's probably good, if it just about freewheels,, it's probably not.



I have a friend with a '79 Chevelle, and with the motor at 220*F you could easily hold the fan in your hands while the motor was running... ( bad idea to hold the blades, and start the motor)



Merrick Cummings Jr

 

[Huff N Puff]

The best test for a fan clutch

Is to watch A\C high side pressures,because 134a freon is extremly sensitive to the air flow thru the condenser. A good fan clutch should keep the high side pressures below 275psi. Merv

 

[WestTN]

check clutch

Use a blanket to cover the radiator front. Set the engine on high idle and wait. When the fan clutch temperature reaches about 205 degrees it will cycle in. You will easily feel and hear the difference. If it does not engage, replace it.

 

[ProspectorTim]

Re: I thought the Chirp was

Originally posted by hammersley

on the main crank as the engine stops Right Now and the belt continues to turn causing the chirp. I don't think it's at the fan pulley.

Right, the chirp is the belt ... but on my truck it doesn't *always* chirp. When I was checking out the fan clutch I noticed that when the motor is hot and the clutch is ingaged it chirped every time I shut it off. When it was cold and the clutch was not engaged, it didn't chirp. I guess stopping that fan puts a lot more load on the belt.

 

[jtwcummins]

When started after setting overnight the fan should sound like an airplane taking off. It will go away in a few hundred feet of driving.



The high side pressure in a/c system is a very good test. It also points out that a bad clutch fan does more than allow overheating. Can cause leaks in seals in a/c system.



Several makers sell heavy duty clutches, but be carefull, HD is not necessarily diesel duty

 

[IWeiny]

Question

Are the fan clutches electric then? I have heard mine come on and yea, you know when it does but it does cycle on then off so how do they work?

 

[rblomquist]

Originally posted by jtwcummins

The high side pressure in a/c system is a very good test. It also points out that a bad clutch fan does more than allow overheating. Can cause leaks in seals in a/c system.

Ok, is that if you have a fan that is on all the time or a fan that never engages. Funny thing about this thread is my 134 was out of the system completely at the begining of this summer, I filled it up and it's still going now however, I need to check the pressure again to see if it's dropped.

 

[jtwcummins]

The fan clutch is thermal. It uses a viscous coupling and the heated air thru the radiator causes the clutch to lock up and unlock as the temp changes. About 180-190 the fan should be engaged and very obvious. It takes awhile after starting a cold engine for the fluid to start working, that's why when first started it is fully engaged.



Even with the noise it might not be totally functional. I generally put gages on a/c and watch pressures