This is for my 1981 240D, running R-12. The compressor seized a few years ago, but it broke the belt, and didn't put junk in the system, fortunately. Put a new one on there, and it works great - holds charge, cools well, etc. I don't drive the car a ton though...
The other day I was driving it and was hearing some sort of a rubbing sound, but there was no squeal. That sound can be heard here, primarily in the second half of the video:
Today I was driving it, and noticed that when the compressor was engaged, I got a bit of a squealing noise. Not entirely sure if it was belt squeal, or more like a pump squeal, like cars with bum PS pumps sometimes make when starting cold. ALL belts are OE Contitech belts (either the ones with yellow printing or the ones with green printing and the MB star), and all look great.
If I disengage the compressor, there is no belt squeal or other noises.
Is this as simple as a sign of a bad belt? It is a number of years old, even if the car isn't driven much... Or is it a sign of a more significant issue forthcoming on the compressor or clutch?
Correct. Was OE fit on these cars.Works fine with R-12, ok with 134a.
The Harrison R4 is a terrible design, Mounting them them with flimsy steel brackets is almost a guaranteed noise maker. GM started using Aluminum Brackets for R4's in 1993 & three brace struts to quiet them down.
The belt squealing could be many things, Incorrect belt tension, Glazed Belt, Oil Slugging from to much refrigerant oil, Wrong size belt groove for the series belts your car takes, Some diesel engines use the wider "industrial" V-Belts.
With only 4 pistons, This compressor is harder to "start" than a 6 or 7 piston compressor, So you have that working against you!
As Chris142 alluded to......A Sanden SD-7 swap is ideal!