This is not good...

[oilslick]

I rebuilt the vacuum pump on my 240D (82) and I must have done something wrong, obviously! I lost ALL vacuum tonight and I mean ALL vacuum. I looked under the hood and saw the problem!

First off- my vacuum pump does not have the "diaphram" it has some sort of piston, o-ring, band, sorta thing. I put it all back together like I thought I was supposed to (only way it would go) tighter than "dick's hat band" but tonight the nut on top of the piston came right through the top of the pump! With the engine running you could see the threaded end of the piston shaft going in and out of the hole it created when it went "south".

What could have gone wrong? Could it be a problem with the end of the IP? I give up!

BTW, I was under my MB yesterday and did notice a tag. It had stamped on it- "MADE IN HELL"

[leathermang]

OK,, start back and review ... and share if you think it might help.. all the steps you went through.... did you rebuild it on the engine or take it off ? I am only familiar with the type I have on my 80 240.... so I am just trying to think generically...
Did you have any manuals to go by when you did this... I know that on mine the pistons are supposed to be in a certain location relative to the rubber diaphram when it is reassembled.. what did you do exactly to rebuild it... what did the parts you replaced LOOK like.. ? IE.. what was the ' failure mode'.... a rip , a leak, something metal worn ?... that sort of stuff... I suppose you can not take a digital picture of the present situation ?

[oilslick]

No- as far as pictures. It seemed to be a straight forward procedure. I am stumped.

I will tear into it in the morning. I don't have any manuals that give any rebuild information so I had to play it by "ear".

Oilslick

[jassz]

What could have gone wrong?

You're scaring me oilslick! This what we're supposed to be doing this weekend! To that end, my husband removed a vacuum pump such as you describe from the parts car tonight. Like the one in this picture right? I had him read your question, and he's wondering if you could have aligned it wrong? There are three possible spots in which you can secure it (I think that's what he said)... maybe you picked the wrong one and there was no where for the piston to go but out the other side? You aligned it as though the car was made in WEST hell, but it's actually from EAST hell, which is to the left a quarter turn.:p

Must have made a helluva racket!

Sorry I can't help you more, but feel better knowing you may have prevented someone else from doing the same thing.

[leathermang]

I will be right back... have to go get my magnifying glass to see that picture... you worried about taking up too much bandwith Nat?

[240_Dizzell]

Hello,

This is my first post, so please exuse me if there are any errors,

This very same thing happened to me on my 240D, the problem is
that the center nut, which holds the piston down, was not adjusted properly. The MB manual calls for a special tool to adjust
the roller bearing and spring on the back. Since I did not have that tool, I bolted the pump back on the motor (leaving the front plate off) so I could see the piston move back and forth. On the front of the pump you will see a beveled mark. Turn engine over several times by hand and adjust center nut until the top of the piston meets the bottom of the bevel....

hope this makes sense

[leathermang]

Welcome to the forum.... most of the time the first post is " help"... instead of being able to help someone else... Bravo.

[240_Dizzell]

Oh,

I forgot to mention, that after I adjusted the center nut. I removed the pump from the motor to put the one-way valves,
and Gasket back on. Be sure the slotted screws which hold the
front plate down are tight, otherwise your precious vaccum will
be leaking

[oilslick]

I put another pump on, from my parts car. Works like a charm!
I appreciate all the hints and concern!

I love this forum!

Oilslick!