Engine side Radiator side
Diesel Chevette clutch fan
I have always noticed that my clutch fan "freewheels" for an extended period after shutting off the engine, and was a rather quiet unit. Usually, the freewheeling is a sure sign the clutch unit has failed, as is a lack of air flow. Another sure sign is an oily residue on the clutch unit, and fan blades. ( Engine overheating is another sure sign ! ) Since my particular Diesel Chevette runs a LOT better when the engine is hot, I gave this item rather low priority, and didn't get around to replacing it for a while. I don't know if the engine was overheating, but I don't believe so. It seemed perfectly content to run just fine in the hot humid Ohio Valley weather, and perform admirably. If the engine had given me any signs at all that it was running hot, I would have attended to this matter much sooner.
Engine side
Radiator side
As it turns out, one of my customers has four Diesel Chevettes in his herd of cars, and since they are just rusting hulks in a field, I asked for the clutch fan units as partial payment for a job. I figured I would get one good one out of the bunch. He brought me two complete clutch (with) fan units, and they were a LOT stiffer than mine. After replacing the clutch fan, I can assure you that this is a very noisy unit ! If yours is not making some serious "fan noise" at higher RPM, your clutch may be *bad* like mine probably was. I noticed some serious air movement at idle speed now which was noticeably absent before. The fan noise is somewhat objectionable at higher RPM, but doesn't seem to affect engine performance. It has been my experience in the past that noisy fans seem to rob horsepower, but this car seems unaffected for whatever reason. No discernible difference in performance.
Now I don't recommend that anyone else ignore their clutch fan like I did for a while. After all, GM must have had a good reason for installing a large 3 row radiator, and a very high air flowing fan. I would like to cut down that noise a little. :-)