Can the vacuum pump be tested/checked off the engine? If so, can somebody please post the procedure. Any info will be appreciated.

You hook a vacuum gauge to the tube that scews onto the brake booster and vacuum pump. The vacuum guage goes on the steped attachment and with the car running it should be 20hg and higher.

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1986 300SDL, 211K,Dealership serviced its whole life
1991 190E 2.6(120k)
1983 300D(300k)
1977 300D(211k)

To test the vacuum pump off the engine, you would need some way to exercise the lever arm that has the ball bearing on it. I could see making a jig to which the vacuum pump would be bolted and a long lever that would push on the ball bearing as you pulled down on the end of the lever. This would be a class-2 lever, if I remember my ancient physics lessons correctly. The spring in the pump is fairly stiff, I'd want a lever that is two or three feet long. With that setup created, you attach a vacuum gauge to the pump inlet and pump away. I don't know how much of a vacuum you can pull "by hand" but at least you'll be able to detect a complete failure.

Jeremy

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"Buster" in the '95

Our all-Diesel family
1996 E300D (W210) . .338,000 miles Wife's car
2005 E320 CDI . . 113,000 miles My car
Santa Rosa population 176,762 (2022)
Total. . . . . . . . . . . . 627,762
"Oh lord won't you buy me a Mercedes Benz."
-- Janis Joplin, October 1, 1970

Oracle, Jeremy, Thank you both for your time but with my limited knowledge and skill level, I'll just install the pump on the car and see if it's OK or needs rebuilding. A friend gave it to me but is unsure if it's operational or not. Thanks again.