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Old 08-30-2001, 01:49 PM
Registered Diesel Burner
Join Date: Aug 2001
Location: Northern Virginia
Posts: 2,911
Question "Extra" Parts found in Vacuum Pump - 300D

Sounds like a classic problem, doesn't it?

I had an episode of lost vacuum on the '82 300D, which uses the mechanical vacuum pump mounted on the front of the engine. This was not a gradual loss, and it was a big problem because the car lost its power brake boost. (Quite a surprise I might add - fortunately I was not in much traffic.)

I started pricing vacuum pumps - but noticed the front cover and decided to do an inspection before giving up and ordering a new pump or a repair kit. After taking off the cover, I removed the upper valve which allows air to be drawn into the pump from the car's systems, but not the reverse. These valves look a little bit like a large hearing aid battery (in shape). Behind that valve I found some "extra" parts which did not appear to belong - something that looks like it might be a check valve and a small spring. The check valve thing was just the right diameter to block the vacuum pump valve. Removal of the "extra" parts and reassembly of the vacuum pump solved the problem.

Because of the diameter of these "extra" parts, there is a limited number of systems they could belong to such that they could travel down the larger diameter vacuum line to the pump. I'm thinking maybe a check valve in the brake booster or somewhere in the large-diameter vacuum line.

I could post a picture of the "extra" parts later if anyone thinks that would help solve the mystery. I'm worried that these parts should serve a function that might be compromised with their loss.

Any experience or ideas here?

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Old 08-30-2001, 01:56 PM
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Not to worry...the pieces came from inside the fitting where the metal line attaches to the vacuum pump. It's a sort of check valve...though not a very good one...and its loss isn't significant in the system's operation.
Randy D.
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