The orifice on the back of some compressors is indented, rather than flat as with the original. This requires the use of sealing gasket discs in order to mate with the original manifold. The problem that some (including me) experienced, is that some kits didn't include the proper gasket disc for our MBs. I ending up ordering the disc from NAPA. I understand that most of the kits that ship now have the right discs I think one is green, and the other - the one I had to order - is yellow/brass colored. Once installed correctly, no problem.

BTW, on your original question, avoid Four Seasons compressors, or any remanufactured one.

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Tjohn

82 300 SD
77 450 SL (gone)