I am wondering what the consensus is on replacing the pump diaphragm - in car or on my bench? If I do it in car, how easy is it to get the 8 screws off and that part out of there with the radiator and fan in the way? Has anyone done it this way? I was told it was easy peasy. Or am I better off just taking the whole pump off the engine? Thanks in advance!

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1980 240D 260k miles , the last car I will ever buy

in car

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Current fleet
2006 E320 CDI
1992 300D - 5speed manual swapped

former members
1984 300D "Blues Mobile"

1978 300CD "El Toro"

Thanks, I reck'n I will do it while it's attached to the car, didn't know if there were any things to watch out for doing it that way. Any clue as to why MB used standard slot screw heads on that part instead of hex or metric bolts? I have adjusted my valves a couple times, is this project (diaphragm) as easy or involved as that? From a vid I say a fella had a heck of a time getting the diaphragm off..

Matt-
Perhaps some of the details I put in this thread would be helpful. Not sure which car you have, but no doubt your experience will be similar. I did this before I ever adjusted valves, and found it pretty straightforward as a beginner. Adjusting valves seemed easier to me later when I got around to it.
Vacuum pump diaphragm replacement, a beginner's perspective

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1968 220D, w115, /8, OM615, Automatic transmission.
My 1987 300TD wagon was sold and my 2003 W210 E320 wagon was totaled (sheds tear).

You need to install the diaphragm under pre-load. If you haven't got a tool to do that on the bench, replacing the diaphragm is better done on the car (you can pre-load the diaphragm by turning the engine so that the rod is in the upmost position.

Tool:

This was on a Piston Type Vacuum Pump.
My Screws were corroded in place.
I broke off 2 and after that had to use Penetrating Oil and Heat to get the others off without breaking them.

That does not mean that will happen to you; but, using some sort of Penetrating Oil would not hurt.

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84 300D, 82 Volvo 244Gl Diesel

Shortsguy: perfect, that's the input I was looking for. Thanks. I'm replacing the diaphragm, valve, and a brake caliper this weekend, fun fun fun... Did you clean out your lines while you were at it? I heard I can use brake cleaner, but don't know if thats too caustic. Perhaps using alcohol would be better... There is wet oil in all the lines under the hood (at least in the grey and brown one's, less so in the yellow and green).

I cleaned the vacuum hose to the intake manifold with brake cleaner and it got out most of the oil. It still was stained, but air flow could move easily. I actually replaced the hose to the brake booster, as it was less than $20 from the dealer, and seemed money well spent. My old one was pitted from age and very yellow. The brand new one is whitish-clear.

Please be sure to follow Govert's advice to preload the diaphragm during installation. As he says, it is still possible to do without removing the entire pump. My understanding is that the diaphragm won't last very long if you don't do this.

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1968 220D, w115, /8, OM615, Automatic transmission.
My 1987 300TD wagon was sold and my 2003 W210 E320 wagon was totaled (sheds tear).