I'm looking for a part that is the seal for the vacuum exhaust tube from the
vacuum pump to the air cleaner.

I've pointed it out in the attached pic.

1979 NA 300D

Attached Thumbnails

 

It is called a grommet. Nothing special about it. You can probably pick one up at any auto parts store.

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actually the air is flowing from the pump to the air cleaner. It's pumping the air away from different systems in the car hence creating vacuum. On later models they did away with this hose and had the pump exhaust into the crankcase.

doh!

Grommet is NLA, best option is to pull one a good used one from another air cleaner lid.
The EDPM rubber used by MB is remarkably long-lived and will typically outlast a new aftermarket rubber grommet.
W123 - Need Part #

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78 W116 300SD 'Desert Rose' new as of 01/26/2014
79 W116 300SD 'Stormcloud' RIP 04/11/2022