I have replaced the A/C compressor on the W210 with M104 without removing the motor mount. In fact, there was plenty of room, so I'm not sure that it is necessary to remove it.

Why would the mechanic replace the compressor for high side running too high? To me that would indicate more of a blockage or TXV problem. If the compressor was shot, it would tend to have trouble creating any type of high pressure.

As for the noise, my E320 also makes a rubbing/vibration noise when the A/C is engaged. That's because the compressor is shot. It still works, but likely has been damaged by very high pressures that caused it to vent refrigerant out of the drier check valve. This is because the PO was driving around with a failed aux fan assembly and shot radiator fan clutch. I have repaired everything but am waiting until this compressor bites the dust before I replace it. Who knows - it may last for quite some time.

My opinion is that either the compressor is faulty (noisy bearings or pistons) or it is possible that the mechanic did not use the correct type or amount of oil.

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08 W251 R350
97 W210 E320
91 W124 300E
86 W126 560SEL
85 W126 380SE Silver
85 W126 380SE Cranberry
79 W123 250
78 W123 280E
75 W114 280