Had the sam thing happen to me, but in the front yard. drove in the driveway, turning around by the barn and it went to the floor. I did have a problem that I had to add brake fluid to it every once in a while. never ay leaks.
I pulled off the master cyl and the booster was 1/2 full of brake fluid.

so I replaced them both. was cheap insurance replacing both for me thinking about what they do on a daily basis.

If it is just the master, easy fix. two bolts and two brake lines.
it is the booster, there are 4 nuts to remove under the dash that bolt the peddles to the fire wall. top left can be a fun one to get to. and the pin that connects the booster rod to the brake lever.
The nuts I believe are 13mm.
Charlie

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there were three HP ratings on the OM616...

1) Not much power
2) Even less power
3) Not nearly enough power!! 240D w/auto

Anyone that thinks a 240D is slow drives too fast.

80 240D Naturally Exasperated, 4-Spd 388k DD 150mph spedo 3:58 Diff

We are advised to NOT judge ALL Muslims by the actions of a few lunatics, but we are encouraged to judge ALL gun owners by the actions of a few lunatics. Funny how that works