PeachParts Mercedes-Benz Forum - View Single Post

Jeremy5848 · #7 06-14-2011, 11:07 AM

Quote:

Originally Posted by todieselornot

What are the signs of a failing vacuum pump? I can hear mine running when I cycle the door locks and sometimes there is a delay when opening the trunk using the inside switch (it opens when the sound stops). What extra expense would one expect if it grenades?

That depends on which car you have. The vacuum pump on the engine is different from the vacuum pump the operates the door locks in 124s, 126s, and others. That vacuum pump is in the trunk or under the rear seat. Failure would not damage anything else. You could have a failing pump or simply a leak that would cause the trunk lock to be slow.

The vacuum pump on the engine can, in failure, dump bits of steel into the timing case, potentially jamming the chain, which then breaks. This leaves one or more valves open to be crushed by their piston as it comes up to TDC. Engines have been ruined by such a failure although I suspect the risk is not all that high.

Early 124 diesels had a vacuum pump with an open ball bearing that could come apart but later models and all those retrofitted (like mine) have a sealed bearing. The 606 also has a sealed bearing.

I have been discussing this subject with forum member Sixto; our position is that, so long as the engine's oil has been kept clean, there is no reason, lacking a documented history of vacuum pump failure, to change the pump just because there are a high number of miles on it.

Jeremy