Fan clutch failing?
 

My 92 300 TE is making a fair amount of noise at the front and it doesn't seem to be either the water pump or the air pump.

Is there a way to test or diagnosis the fan clutch bearing when you think that might be the problem?

What kind of noise?
If its screeching already... look at the bottom of the pully's travel to see if it is in contact with the crank pully (beneath and to the right [looking down] of it) (while running).

Also: you can try to rock it front to back (engine off ;) ) to see if there is any play... the bearing is pretty sealed up so I don't think spraying wd something on it would do much to releve the noise as a test.

Hard to describe noise, not screeching at all, more of a whirling sound. Used stethoscope to listen to different acessories and the pulley in the photo seemed loud, but I did not know where to listen for fan clutch bearing noise. I put stethoscope where you see the red mark in the photo.

Doesn't seem to be any excessive play.

Sometimes it's best to remove the belt & spin each pulley individually, to determine the offender.

That would be the one.

You probably have some time before it goes (they usually give a lot of warning noise before they finally fail)

Dont think it can be serviced... need to replace the bearing bracket that bolts to the block (under the distributor cap) and the pully.

But you have a little time to get to it most likley.

So you don't think it's the fan clutch but that pulley?

Is that pulley called Acc. Belt Idler Pulley?

The bearing is part of the bracket...
http://catalog.eautopartscatalog.com/mercedesshop/sophio/wizard.jsp?partner=mercedesshop&clientid=catalog.mercedesshop&baseurl=http://catalog.peachparts.com/&cookieid=1FX0MB1RS1PN0VD649&year=1992&make=MB&model=300-TE-001&category=G&part=Fan+Clutch+Bearing+Brkt
The pulley bolts to it as does the clutch through the front...
Noise usually means bearing.

It could also be the belt. A splash of water can check it, and its the easiest test.

The above is correct.:) The bearings sound like ball bearings mixed with sand, no grease at all. I've ordered the bearing bracket and the small idler pulley too. My cost for the bearing bracket is way less than Fastlane, it's $88.50.

I don't think there is anything wrong with me fan clutch.

While you are in there I would also tend to the belt tensioner and belt tensioner damper...unless you have record of it being replaced in the not so distant past.

Check your H2O pump as well, see if you can discern any play.

Jonathan

Vehicle now has 133k miles. Service records indicate the belt tensioner and shock were done at 76K miles, they seem fine. The water pump was done at 57K which seems a little early. It's not leaking and the bearing turns smoothly and quietly.

I just bought this 1992 300 TE and am going over it to replace numerous items. See list below. I have another 1992 300 E so I have a general idea of what breaks and when. As I recall I replaced the belt tensioner on my other 300E at about 80K miles with the water pump being replaced about the same time.

Work done immediately prior to purchase by seller:
A/C blower motor
oil sending unit
driver’s side door window motor
Climate control unit

Work done by me:
Coolant reservoir
coolant reservoir cap
5 coolant hoses
thermostat & gasket
radiator overflow plug
coolant
Acc mono valve
auxiliary water pump
fuel filter
oil filter
oil and oil filter
power steering fluid flushed & filter
hydraulic fluid flushed & filter
transmission fluid, filter, & gasket
rear diff. fluid
wiper blades: front, back & headlights
distributor cap, rotor, suppressor & o-ring
ignition wire holder
6 spark plugs
voltage regulator
battery & battery hold down clamp
refinished battery tray
2 breather hoses
air intake hose
hood silencer pad
rear muffler & muffler clamp
4 exhaust system hangers
flushed brake system
adjusted front bearings
rear shock bump stops & shock boots
2 accumulators
replaced trim piece by front seat
rubber covers that attach to driver's side & passenger mirrors

Waiting on these parts:
Acc. belt idler pulley
fan clutch bearing bracket

Photo of old fan clutch bearing in bracket. No grease at all. Seal that was at back of bearing just fell out. I'm impressed it did not seize.

is it common for the belt tensioner to break? Should I replace mine while I have the belt off?

it doesn't so much break as get weak.. Usually if I'm going into the front of an M103 for some major service and there is no record of the tensioner having been replaced I replace it. The dampers usually get a flat spot in them..90% of the action will be damped quite nicely but where it operates most frequently will be very easy/lacking in damping.

If you look at your belt while the car is running it should look nice and smooth, if you see a healthy amount of vibration you know it getting Tired.

Jonathan