Slow moving fan...

[sleepdoc38]

Hi,

I have a 1991 190E 2.3. I've noticed that the fan moves very slowly and I'm suspecting that the fan clutch is the problem. However, I'd hate to buy a new one only to find that it was something else. How can I easily determine why the fan is spinning slowly before getting into a costly repair?

If in fact the fan clutch is the problem, is that something that can be changed easily? By removing the shroud, the fan is fairly accessible. But I don't know if the clutch is on the water pump side of the belt or the fan side.

Thanks,
Sleepdoc38

 

[andy_k]

I think you'll find it's a thermo coupling so unless the engine is hot the fan will move slowly.

to test the coupling safely there's a simple test you can do with a carrot

when you first start the engine place the carrot into the fan blades and see if it stops the fan - it should do

let the engine get hot - you need the thermostat to open so you are looking at about 105 degrees - at that point try the carrot again and you should in theory end up with diced carrot (and a very graphic reminder of why you didn't use your fingers) if the link is working properly.

If the fan blades stop when the engine is that hot then there's a pretty good chance the coupling is knackered

HTH

Andy

 

[sleepdoc38]

Hi Andy,

Is the thermo coupling the same as the magnetic fan clutch?

I'm in the States and didn't know if the terminology was different here.

Thanks,
Mike

 

[andy_k]

no the magnetic fan clutch is controlled by a sensor attached to the engine (thermostat housing?) .

Test the coupling bypassing the sensor (just short it out)

Andy

 

[sleepdoc38]

Hi Andy,

I reached around behind the fan belt and found the two wires that connect to the magnetic clutch. They seem to be intact. I'm not sure where to find this coupling, though. If you can give me some directions as to how to do this and then short it out, I'd be very appreciative.

Is it possible then that a faulty thermostat could keep the fan clutch from engaging? I just purchased a used, but working fan clutch on eBay for only a fraction of the retail price. But changing the thermostat is much easier to do. And I'm sure that mine is stuck in the open position. It was my understanding though that the thermostat only controlled the flow of coolant into the water pump. Does it also control the fan clutch?

Thanks again,
Mike