I picked up an '81 300 SD three weeks ago. Over the past two weeks I have had a problem with the belts squeeling. It seems to happen only once the car has warmed up a little, and happens sitting at idle as well as while driving. I [I]think[I] it's happening just when the air conditioning is running, but here in Florida that is almost always.

I checked the belt tension, and that seemed fine to me. I applied belt dressing, with little improvement made to the intermittant squeel.

Yesterday, the squeel stopped. I think that was due to the compressor belt breaking.

Do I have a compressor that has the bearings seizing up? Is there a way to check it?

On prior inspection of the belt, it did not appear overly worn, but it certainly wasn't near new either.

I'm very mechanically challenged / ignorant. I would hate to go through the hassle of changing out the belts only to have the squeel re-appear and break another belt. Any suggestions are greatly appreciated.

I would also like to know if anyone can recommend a reasonable MB repair shop in the Vero Beach, FL area.

Thank you

Try to turn the compressor by hand. If you can't then that is probably your problem. I have seen the clutch lock up on them doing the same thing you are describing.

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Jim

A belt doesn't just break for no reason. Examine the belt. Was it on the vehicle since it left Germany? Is it an aftermarket POS? Is it a US equivalent that is narrower than the specified metric belt? Are there signs that the belt should have been replaced long ago?

If so, then install a proper new Continental belt that fits the pulley properly. Tension it to the required level and try it again.

If the clutch is seized, you'll see smoke pouring out from the new belt and the noise will be horrendous.

I know that sound, happened to mine a week ago.

When you turn it by hand, make sure you are turning the center part of the pulley, not just the outer portion. The outer portion should turn easily (without a belt). The center will be harder to turn, but it still should turn by hand.

Thank you for the tips. I outer part of the pulley moves freely when I turn it by hand, but I didn't know if that really told me anything or not, as I thought it may only be seizing up when a clutch inside the compressor was engaging. Tomorrow, when I have daylight, I will try turning the center portion of the pulley. As you can tell, I am pretty ignorant about this.

As I said in the original post, the belt was not new, but at an earlier inspection I did not see any signs of gross degredation or undue wear. Not enough left of the belt now to really tell anything.

I never did see any smoke pouring out while in motion or at idle.

Craig,
You said you had the same thing happen to you a week ago. Did it turn out to be a compressor problem?

My compressor seized in a big way, the entire front of the clutch was missing when I stopped. The clutch bearing also seized and stopped turning, resulting in the belt pretty much melting off. I cut off the belt and drove home, I now have a new compressor installed.

Craig,
I tried your suggestion first thing this morning. The outter part of the pulley turned freely. The inner part was much stiffer, but still turned. I applied pressure by hand against the edge of the triangular shaped plate on the front of the pulley. I turned it a couple of revolutions both clockwise and counter clockwise.

I hope this is a good sign that maybe I won't be wasting my time putting on a new belt.

Thank you

If you're lucky, the belt was just old and it broke. If you're not so lucky the compressor seized and broke the belt. Let us know what you find.