I considered for a while replacing the fan motor bearings (they are bronze
oilite and wear out) with some ball bearings, but decided that the better
solution would be to replace the whole fan, motor and all. I got one from a
wrecker for $25, and it's worked fine ever since.
Somebody else mentioned a growling sound coming from the heater at all
speeds. If that's happening, be advised that it sometimes goes away when the
car warms up, but eventually on cold days it degenerates into a really awful
squeal that will not go away no matter what speed you put the fan on. Better
to fix it while the weather is still reasonably warm.
Egon Frech
505 STI V6, 1987