The overboost protection valve is there for a reason. It's probably just gunked up and needs to be cleaned out or replaced with a new one. A new or clean valve will give your the great performance associated with bypassing a dirty valve, but without the risk.

__________________
'81 MB 300SD, '82 MB 300D Turbo (sold/RIP), '04 Lincoln Town Car Ultimate

Sooner or later every car falls apart, ours does it later!
-German Narrator in a MB Promotion Film about the then brand new W123.

I'm looking for a reasonable transmission rebuilder in or around Metro Detroit (Michigan) for my '84 300CD. Will probably need the neutral safety switch as well as the Valves adjusted also. Thanks! -Byron

I wonder if the brake booster is indeed bad. Pulling off the master cylinder and cleaning out any brake fluid in the front section may be all it needs. The rear seal on the master cylinder leaking out is very common.

I think although you should check that in most cases the booster is swabbed out and a new or reconditioned master cylinder installed. The booster itself is an expensive part new. A unit from a salvage yard should suffice if required.

They do not fail often enough to make a junkyard purchase too risky. If for example the power brakes are working now even with the leak the booster is still good.

There is one of four nuts that retains the booster that is in a mediuim difficult place to access. Look into the archives for the best tool combination to change it if you have too.

I just got back from the auto parts store.

Bought all new rotors and pads

New transmission fluid filter

7 quarts of Castrol import ATF (can someone tell me how many quarts it really takes? i was told 4 to 7 so i took 7 quarts.

The brake booster was 87 dollars so i already made purchase of it

Master cylinder i already had.

And now to barrys point, like i said what he told me it could be full of brake fluid in there, the pedal is somewhat hard to push.. in the past i have lost all pressure and have gained it back. my parents drive it everyday barely going past 2500 rpms, ME on the other hand i put that thing to the floor and she what shes got! i notice after i drive it i smell brake fluid everytime... when my parents are done driving it hah not a scent... you also got to remember thats the orignal 24 year old booster.. still functioning well

Haha ill have to get back to you on that one my friend! I prefer fixing my own things but if your willing to come to Pennsylvania you sure can

What can you use to clean it? WD-40? and i know it works cause ive hooked up a manual air pump to it and it clicks when i put alot of air through it

My bad as for some reason I thought the brake booster was way more than 80 some dollars rebuilt or new. With no consistancy on the power brakes yes I would replace it as well as a possible potential cause.

I just do not know the overall effects of having brake fluid in the booster long term. Then checking for vaccum issues if the problem surfaces again.