'88 300 SE Fan clutch
 

Just wondering how to tell when to change fan clutch. How can you tell when it is going bad. PO had new radiator installed and I just don't want the fan to mess that up, Car has approx 138k miles on it. Some engine noise at front. Have changed tensioner pulley and idler pulley and alternator. How do you isolate noises from different components, ie power steering, ac compressor, water pump, and fan clutch, when they are all tied together with one belt? Thanx..........

You can isolate noises by using an automotive steathascope(sp?) or my fave, use a standard broom. You put the handle end on the suspect device and listen on the broom end.

Thanks for the reply,
How do you get that broom onto the fan clutch, or stethoscope for that matter?

Carefully.

Yeah Douge, REAL careful!!

Hello everyone,
This is still a standing question. Any answers??? Thanx.........

Again, use an automotive stethoscope. The fan clutch should be changed when it is no longer effective. It's filled with silicone.

So what should we be listening for (and where)? Obviously not the clunk clunk clunk of the fan hitting the broom! :confused: :)
With the fan shroud on, it's a little difficult getting a broom handle down on to the centre of the clutch.

The fan should be stiff to spin when the engine is hot. If it free wheels, there is a very good chance that the fan clutch has had it. My 260e has a whistling sound coming from the alternator area. The alternator has a lot of free movement on the pulley indicating the bearing is on the way out. If the tensioner is not installed exactly correctly you can get a squeal squeak type of noise that seems to come from the fan belt.

Thanx for the replies guys,
Where do you place the stethoscope on a running engine to isolate fan clutch noise. The "real estate" between fan clutch and water pump seems so close. Doesn't the noises of one or the other transfer through the metal of the engine. I am already aware I should change it if it is bad. Just trying to figure out if it is bad (thus my original question). I have already installed tensioner pulley, idler pulley, and alternator (correctly) so I have already ruled out these items. Again, thanks for your input........

I agree with Ivanerrol, the fan blade should be difficult to turn by hand with the engine warm/hot. If the fan spins free (with hot engine) then the fan clutch is shot.

ok, I'll try turning fan with engine at normal op temp. tomorrow. Thanx.......

i dont see much room on my 90 300se, any ordinary wrench will be impossible to reach the nuts & bolts, i talked to merc dealership, they say there's a special wrench to undo it, anybody knows what it looks like, shape etc. TIA

My 126 300 sd was tight but not impossible to change the clutch assembly.
I did install one from a 560sel, the air volume was unreal, so much air blowing to the point the insulation foam under the hood disintegrate pretty soon. The car eas sold not long ago.

Now my 90 300se I do notice the temp can get hot in crawling situation , luckily the dual electric fan do kick in at 100 ish or else the result will be precipitous.

testing clutch
 

roll up a newspaper and with the engine cold you should be able to easily stop the fan and listen for any any noise.
when hot the fan will not stop with the rolled paper. (proper operation of clutch)
if the engine runs very hot the cut in point of the clutch can be brought down to a lower cut in point by shimming the temperature thermoplate on the clutch (1mm).
the tool is nothing special just a 4mm or so thicl rod bent ay right angle about one 1".
mak
300se

SD300-where did you come from? yikes