Hey guys, need your help here,

i have a 1982 300DT here and it had a vacuum leak in the brake booster. so i replaced it and now my brake pedal is sitting up way to high. in fact it was so high that it broke the brake light sensor off its pot metal bracket thing.

I stupidly threw away the old brake booster and did not compare the new booster to the old but are there differences between brake booster fork arm lengths? or is there some adjustment i can do to the brake booster?

I tried searching this topic but couldnt come up with anything, maybe im searching the wrong stuff. Please help! as now my brake light is constantly on and i dont want to jpweld the sensor back until i know its in the right place.

any advice is welcome! let me know! thanks guys

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1978 300D

Always remove the pedal sensor when replacing the booster (all cars). You don't want the pedal to bottom-out on the sensor. The sensor has an adjustment to position it properly after the pedal is in its normal resting position.

"Booster fork" must refer to "brake rod". Perhaps you got the wrong booster PN. Many boosters have an adjustable tip where it contacts the MC piston. If so, you need to adjust that. If too far extended, the MC piston won't retract enough, sometimes not enough to expose the "refill" ports, plus the pedal will sit too high. You want it to just touch, with no play. I had my M-B MC & booster apart, but don't recall. But, Google Images would answer that for you.

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1984 & 1985 CA 300D's
1964 & 65 Mopar's - Valiant, Dart, Newport
1996 & 2002 Chrysler minivans

FYI just to close this issue. I had replaced the brake booster on the 1982 300DT with a new unit. This new unit was a 10" booster. it's arm/fork (that attaches to the brake pedal) was too long and broke my brake light switch bracket.

I have since obtained a new 9" booster that came on the earlier cars which worked perfect and had the correct length arm. Also replaced the brake pedal bracket with a good used one. brake lights now work YAY!

Just figured I would leave this here for the masses in case anyone else ran into this issue. It was really frustrating not knowing they were different and that all online "fitment guides" showed the newer one should work but it did not.

Now all is well.

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1978 300D