1980 300D

The brake has been really hard since I got her. The vacuum system isn't flawless, but it's pretty good. CC works, locks, ACC is a little wonky, car shuts down, etc... The EGR vacuum line is hanging free, by trial and error I found that state to be the best setting for the transmission (shifts like I think it should) but that's a leak... when it's plugged, though the brakes aren't better... Is there a check valve that might be faulty? How do I diagnose the booster? Thanks a ton!

Ash

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Ash Peltier - tools, truck, tales
---------510-331-4118-----------
1982 240D - (272,000)
1998 Honda VTR1000F(RT) Superhawk Freeway (58,000) "Madrid"
1996 Toyota T100 4x4 (84,000) "Mary Kay"

I was trying to diagnose my brake booster as well. What I really wanted to do was unhook the main vacuum line from the booster and SOMEHOW hook my mityvac directly into the booster. I never found a way to do that, but i did find a generic brake booster test;

With the car off, pump the brake pedal a few times then hold your foot on it. Start the car, the vacuum should build up in the booster and draw the pedal to the floor.