'82 300SD brake booster failure??
 

I am helping a friend with an '82 300SD. When I hook up my test gauge on the vacuum booster line I get a fluctuating vacuum signal that bounces between 0 and 4" Hg (negative obviously). Next when I shut the car off and disconnect the vacuum booster line at the brake booster I hear vacuum "escaping". With the line disconnected at the booster and running the engine with my finger over the vacuum hose where it connects to the brake booster gives me around 15" Hg negative (which I feel is "good" vacuum). It seems obvious that the brake booster is leaking pretty badly and I just want someone that has seen brake booster failure verify this conclusion. It looks like it is probably a pia to replace the brake booster because, based on what I can tell, it is bolted up on the cockpit side under the dash (I hate under the dash work). Thoughts/comments are welcome and are brake boosters rebuildable?
thanks

Brake booster problem
 

Hi Jim,

I have a similar problem with my 82 300D Turbo. How did you deal with the booster? I hooked up a vacuum pump to my booster and it holds no vacuum. A new one is expensive, MB has a booster repair kit for $7 but they don't know what is in the kit and it gets shipped from Germany as no one seems to buy them. Because of this I am not going to order one. I am going to look for a booster at a local MB salvage yard for $75. Hopefully can find one that looks like it was replaced recently and has no brake fluid leaked into it.

BTW, my vacuum pump put out 17"Hg vacuum and I decided to replace it. The new one now puts out 23" Hg. Maybe it wasn't necessary but I was told by a MB mechanic/friend that there should be at least 20" Hg at the pump. He also felt that the booster rebuild would contain the diaphram but that the leak is likely with some internal valve(s) that are not likely supplied in the $7 kit.

Regards,
Elliot