when your brake fluid stars to disappear and you engine smokes, then is the time to have it rebuilt, the pneumatic chamber shouldn't have brake fluid in it, but if you take the big engine vacuum line off and it pours out brake fluid, one of your seals is bad, as for rebuilding, i bought a rebuild a few days ago and it has a sticker that says unit parts ,oklahoma city i dont know how old that sticker is, i cant find it on their web site
