Sometimes you can loose fluid from the MC into the booster, pull 'em apart, and inspect. There is an "O" ring between the two. This may be the case if you can't find the fluid that is no longer in the MC.

I'm not sure how brake fluid can make it's way to the crankcase.

If your booster is failing, it won't hold vacuum. It can be tested by evacuating the booster with a mity-vac, and see if it holds pressure.

__________________
83 SD

84 CD