I'm continuing to work my way through all the potential problem areas on my recently acquired '82 W126 300SD and am about to check the condition of the vacuum pump's cam follower and the drive cam on the 617.950 engine. I bought another vacuum pump (Pierburg #7.20547.50.0) to have as a possible spare to use as a new baseline to operate from if necessary.

I have now found that the vacuum pump on the engine is different from the one just bought and specified by Fastlane for the 617.950 engine from a W116.120.

The old pump has two threaded fittings, one for vacuum supply for downstream systems and the other for a plastic line running to the grommet on the U-turn hose from the air cleaner to the turbocharger inlet.

The new Pierburg pump has only one threaded fitting for vacuum supply to systems. My checking tells me that the old pump is a diaphragm type with several gaskets and the new pump is a piston type having noticeably fewer parts.

Question: Is there any significant reason why I cannot use the newer pump in place of the older one? The grommet at the turbocharger inlet would of course be replaced with a suitable plug. My sense is that I can make the change but any information or opinions to the contrary would be appreciated. Thanks very much.

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Respect, protect, and maintain complex systems - whether natural or of German design, to benefit from their full potential.

1982 300SD W126.120 with an OM617.950 from a W116.120
1984 300SD W126.120 with an OM617.951