Low vacuum reading

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anahataray - 22 Oct 2006 19:44 GMT

I have been having some shifting troubles, and I tested the vacuum at the
main vacuum line "T" in front of the brake booster. I was told that I should
have 21-23 inches HG, but I only have 16. Does this mean my vacuum pump is
bad? I wasn't sure if there was any way to adjust the pump? Thanks for the
help!

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Karl - 22 Oct 2006 20:24 GMT

On what car/engine???

> I have been having some shifting troubles, and I tested the vacuum at the
> main vacuum line "T" in front of the brake booster. I was told that I should
> have 21-23 inches HG, but I only have 16. Does this mean my vacuum pump is
> bad? I wasn't sure if there was any way to adjust the pump? Thanks for the
> help!

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anahataray - 22 Oct 2006 21:46 GMT

>On what car/engine???
>
[quoted text clipped - 3 lines]
>> bad? I wasn't sure if there was any way to adjust the pump? Thanks for the
>> help!

Sorry, 1983 300SD

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Karl - 22 Oct 2006 22:05 GMT

That helps.....

Remove the line on TOP of the vacuum pump. Get a flashlight and look in the fitting on top of the
vacuum pump. Do you see a check valve in it? Or is it an open fitting? More than likely, it will be
empty. If it is, go to your MB dealer and buy a new fitting. It is available separately.
Remove the fan and fan shroud. Remove the screws from the cover on the vacuum pump. Carefully remove
the cover and WATCH the position and the direction of the two check valves in the front. Remove the
top one.
Fish out the 3 pieces of the broken check valve that fell down from the top fitting: a flat piece of
metal with 3 ears [that is the piece that broke], a spring, and a dark grey plastic piece.
The replaceable fitting/check valve is #20 here:
http://www.detali.ru/cat/oem_mb2.asp?TP=1&F=123193&M=617%2E952&GA=722%2E120315&C
T=M&cat=143&SID=13&SGR=090&SGN=03

Part number 004 997 18 72

Available here also: http://www.importeccatalog.com/
Only a buck cheaper than the dealer list price.....

> >On what car/engine???
> >
[quoted text clipped - 4 lines]
> >> help!
> Sorry, 1983 300SD

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Richard Sexton - 23 Oct 2006 05:21 GMT

>I have been having some shifting troubles, and I tested the vacuum at the
>main vacuum line "T" in front of the brake booster. I was told that I should
>have 21-23 inches HG, but I only have 16. Does this mean my vacuum pump is
>bad?

If you're sure there's no other leaks (I'd test right at the pump) then yeah
that's weak.

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Need Mercedes parts? http://parts.mbz.org
Richard Sexton | Mercedes stuff: http://mbz.org
1970 280SE, 72 280SE | Home pages: http://rs79.vrx.net
633CSi 250SE/C 300SD | http://aquaria.net http://killi.net

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