PeachParts Mercedes-Benz Forum - View Single Post - 1989 300E w124: I get a grinding, screeching sound whenever I change gears (P, Dr, R)

Richard Wooldridge · #7 08-08-2007, 08:52 PM

I think David hit the nail on the head with the loose serpentine belt diagnosis. The serpentine belt is the wide flat belt that goes around the pulleys at the front of the engine. With the engine OFF, check the tension by pulling on the belt. It should be very taut. If you can twist the belt until it's up on edge, it's too loose. The belt tensioner is the most likely fix, but you could also have a defective belt. If the belt is loose, it will cause the alternator to slip on the belt whenever any electrical load is applied, like the headlights or brakelights. This will create quite a squealing sound. If the belt is loose, whenever you turn the steering wheel while the car is stopped will cause the power steering pump pulley to slip on the belt, causing quite a shriek or squealing sound. Should you turn on the climate control (heater/AC unit), the belt will surely slip on the compressor pulley, causing a loud shrieking noise. My daughter has a Range Rover that had the belt installed incorrectly, and whenever the lights were turned on the belt slipped on the alternator pulley and made an unbearable noise. In that case, all it took was a new belt installed correctly.