Fan clutch diagnosis?
 

A friend of mine has a C series Kompressor 1994 (not sure of the model).
He has noise from the front of the engine that sounds like a metal on metal rattling with a slipping belt. After look at it for him, I thought it was coming from the fan clutch. I assume this model has a clutch because when the engine is off, the fan spins freely. My guess is that the clutch is not engaging fully and is causing the "slipping" type noise.

Is this a common failure? Does this sound like a realistic possibility? From my research it seems that is actuated by a solid state device and not a centripical type device. I know he had the water pump replaced a year ago.

Lastly, if this a fan with a clutch, why would MB do that? What a F'd up, over engineered way to do things. An electric or direct drive fan has been proven for years....:rolleyes:

Electric fans are standard fare for transverse engined cars. Direct drive is simpler but wastes energy when it is not needed. A fan clutch is hardly high tech. and saves energy by only using energy to cool when it is needed to cool the engine.

I don't know how the clutch in that car is activated.

Tom W

Although I have a 300SD and a '67 250S, I've usually had Saabs. With the exception of the OG900's they all had transverse engines. Not one of them had a fan clutch, they all had electric fans. I've had 900's, 9000's and a 9-5. It just seems to me to be much easier and dependable technology than a fan clutch.

The fan clutch engages using a bimetallic strip. When the engine gets hot, the strip flexes and locks the fan to the shaft. Otherwise it will spin freely and save some power. An elegant solution to a difficult problem IMHO. :)

A fan clutch going bad should not cause the sound you describe, nor should it cause the belt to slip. Mine went bad and can caused the clutch to be engaged all the time. The only symptoms were that the fan was really LOUD and the engine ran really cool.

I would look at things like alternator bearings or the water pump.

That is probably a serpentine belt, yes? I would look at the tensioner.

Tom W

that's possible but I've never had a SB slip before (yes i know it could happen). It really sounded like the fan clutch to me. I'm thinking that maybe it got damaged at the last install? I did rock the whole assembly to see if there was play in the bearings but didn't find any.

Fan clutches fail by not engaging or by staying engaged, they seldom make noise, I think.

Tom W