RE: How to Bleed Brakes
Power brake boosters and ABS valves have been known to fail. Damaged brake boosters can even lead to a damaged master cylinder (even if the master's new).Nothing lasts forever. Especially when you have contamination (dirty "brown" fluid) in the brake lines. Before you go too far you should have a look at the brake lines to be sure they have no obviously damp or wet spots on the outside of the lines where they could be leaking slowly. Pay special attention to hoses. If you take a hose and push it lightly one way and the other and see super-small fractures in the rubber (dry rot) you should replace them - they can also cause trouble. If you had brown or black fluid it would have been a good idea to replace everything because the debris can be nearly unable to be removed with all the extra valves - ABS, brake proportioning, etc (it just jams them up). I'm in the process of doinga full brake job on my car 'cause of bad fluid. I'm happy I don't have ABS though. I complain but I really only paid like $450 for the whole deal (power booster to the calipers and everything in between). The most expensive part was the proportioning valve at $190.