AC compressor noise. 1983 240D
 

Many little things are happening to the car this summer, 1983 240D. New tires promted a front end alignment. Adjusted the steering box due to "wondering after the new tires, it was just the alignment so I had to adjust the steering box again.
Water pump started leaking and I did not catch the puddle under the car so it over heated on the highway. Had it towed and I replace the water pump ( running fine now) . Shortly after that, a noise started in the front of the engine. Though maybe the timing chain but diagnosed it today to the AC compressor. Occurs only with the AC on. The noise is the sound of a couple of marbles loose. Sort of a random pattern and only at idle. Rev the engine and it stops. AC pressures are normal for todays temperature. I added 2 oz of mineral oil. Still there. Does not occur when the clutch is disengaged. AC is cold. Vent temps normal.
Last December I replaced the evaporator due to a leak. New R/D, oil for the Evaporator, expansion valve. Flushed all lines and condensor. And now this noise.

Anyone heard this "noise". It is possible the compressor is failing. Don't need that right now. Pressures were 22 Low and 295 High. 95 degrees today.
Vent temps 38.

Thanks for the input.

Dave

I can't explain why, but a loose drive belt will cause a compressor to make those kinds of noises. Mine did the same thing. When I bought a NAPA Kriket belt tension guage and adjusted the belt tension to spec, the noise stopped.

Did you ever resolve this? I have the same noise. 2 marbles loose, or a 3 legged horse walking on cobblestones. Only at idle.

New compressor. New R/D, expansion valve, condenser, a few new hoses, 170 ml mineral oil, 2.6 lbs R-12.

I second a loose belt as the cause. The compressor on my 300 started making this god awful noise at idle, as if the compressor was grinding it's inner workings. Tightened the belt and it was quiet again. Mercedes should have used two belts instead of one on the A/C in my opinion.

Well, I bought a kricket tension gauge this afternoon. We
will see if belt tension is the cause.

All belts were dangerously loose. So much for tensioning belts by "feel".

My Haynes manual was practically useless. It said tension for
A/C and P/S was '50'. Can't be kg, must be pounds. Set both at 50 pounds.

It said the alt belts should be '30'. I couldn't get them equal, so the inner
is at 30 lbs and the outer ended up at about 25.

Most importantly, the noise is gone. Thanks everyone.

You might want to check the bolts that hold the compressor on too..... I would even if the noise is gone, you don't want to loose one of them (not easy to find another).

Retorquing the compressor attach bolts was part of the belt
tensioning exercise. They are all torqued properly.

To close this post.

I installed 2 oz of AC Mineral oil. Check the charge and added a couple of OZ of R12. Based on the outside temp. Installed a new AC and power steering pump belt due to the power steering belt separating. And the sound is gone. Or at least my Daughter has not mentioned it. And yes, she mentions every little noise in the car. To the point that I tell her to turn up the stereo. I am assuming it was the Mineral oil or probably the belt.

Just wanted to complete the post.

Dave