I am new to this sight and in need of some big help.
I was not paying attention when removing my check valves.
My car is a 300D 1977 and the vacuum pump is the bladder style with two check valves.
When replacing the valves should they be crown up or crown down?

I do not know which way your valves go, but if you go to Google and click on advanced search. type in your problem in the discription area and mercedesshop.com in the domain box, the hit enter. This will put you in the forums archives. I have found these to contain a wealth of info.
________________
blindwolf
1983 300D

Thanks Blindwolf I tried that earlier and found lots of info on vacuum pump but not this specific problem. Help please I just finished my second Black and Stormy. One more and this day will be spent.

Have another one or six, you might be alright.....

__________________
If it ain't broke take it apart and find out why.

1983 300SD, 4 speed
1994 C280
1987 300TD wagon
1996 HD Road King

Ride in Peace Eric Peterson, Harley of Macon

thats what got me here in the first place.

It has been a couple of years since I did mine, but IIRC they are installed crown up. I'll be honest though, I'm not positive.

__________________
Sam

84 300SD 350K+ miles ( Blue Belle )

Thanks Sam . I might just have to go with that.

here is the direction of the check valves.Check valve running to the air filter should be crown up. Check valve to the system should be crown down.I hope the pictures will help with the problem of not paying attention.

notice the second picture shows the clear hose leading to the air filter housing.
first pictures shows left side crown up right side crown down.

Attached Thumbnails

   

I replaced the diaphragm on mine (80 300 TD) over a year ago. As I carelessly failed to observe the positions of the check valves I had to figure out how to re-install them. You can blow through them to determine which way they flow or check. Then observe which pipe is the outlet. That's the one that goes to the air filter housing. Make sure the pump sucks on the line that comes from the brake booster and blows toward the air filter. If you can blow or suck both ways through the check valve it needs to be cleaned or replaced. Both of mine were good and still working. Steve