I just re-installed my R4 (after removing every component in the AC system other than the evaporator for leak testing). I looked at the install carefully and come to the conclusion that the only thing that keeps the casing of the R4 from sliding off towards the clutch end of the compressor is the bent sheet metal tab on the casing, not the mounting bolts/ brackets or anything else.

So the big question is what caused your's and Demothen's to explode? They are both brand new R4's, not rebuilt's. Is it a quality issue or operator install error?

The fact that your mechanic says there is no high side service port says he does not know much about the AC system in your Mercedes.

Can you take off the compressor manifold (13 and 15 mm wrench) and take some pics of the parts? There is an aluminum insert in the suction side sealing step washer (the bigger diameter of the 2 tubes) that must be installed. He could have dropped it and not even know about its existence when it was first removed.

The aluminum insert provides support of the rubber seal on the step washer so it is not squished out. On the discharge side, the insert is built into the manifold. On the suction side, it is a free floating piece that can be a puzzle to install for those not familiar with it. Without the suction insert, it is possible for the step washer to leak and and suck in air.

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85 300D turbo pristine w 157k when purchased 167,870 July 2025
83 300 D turbo 297K runs great. SOLD!
83 240D 4 spd manual- parted out then junked