I'm not sure yet the extent of my ABS problem. The ABS panel light has been on for months with not apparent affects to the braking. I lost my brakes recently and noticed I had lost a lot of brake fluid. I topped the system off and bled the brakes once. Voila! I had my brakes back. I suspected by rear wheel cylinders were leaking. Until I replaced them this past weekend, I just kept topping off the brake fluid every couple of days or so (until I could get the money to do the rear brakes). I didn't top them off the last two weeks and I lost them again. Even after I bled the system 4 times, I still had a spongy brake pedal. After driving it about a mile, you got some of the brake power back. By the way, up to now when I bled the system, I just did the quicky bleed with two people - I just bled the fluid straight out the bleeder valve onto the driveway 7 or 8 times.
After I replaced everything except the drums on the rear brakes, I bled the brakes using a clear hose and a clear bottle with some brake fluid in it. (Note: the wheel cylinders were definitely leaking big time) The best I could tell, I got all the air out of the system. The first couple of times on each wheel, the brake fluid was clear with bubbles, then it got light rusty looking, then clear again (you had to look at the level in the bottle changing to finally or you'd think nothing was coming out of the bleeder valve). Also, I had trouble getting the back right metal brake line unscrewed out of the back of the wheel cylinder. It wasn't cross threaded; it just squeaked a lot getting it off. When I was bleeding this wheel, I noticed I had a tiny leak coming from this fitting. I'm replacing that metal line this coming weekend.
Even after bleeding the system twice since I did the rear brakes, I still don't have the brakes back to normal. They are spongy for the first half mile (not quite as bad as before though), then I get them back better than before, but only about 80%. My ABS and my brake panel lights are both on. I've read the site faq and gone to
"The central problem of the ABS-10 system is a leak in the seals of the master cylinder piston. When this leak occurs, reserve pressure continuously bleeds off; this causes the pump to run more as time goes on. Eventually, the pump runs continuously until it burns out. For example, in one person's vehicle, the pump runs for over 5 seconds every 30, whether the person is using the brakes or not. This appears to be the only visible symptom, so watch for it.
Unless you notice that the pump is running every time you press the brakes, there may be no warning of failure - until the pump fails. Then, after a couple of normal brakings, the brake light on the instrument panel will activate and the power assist will disappear. The brakes will still work, but the power assist will be gone. Without the power assistance, it may seem as though you have lost the brakes. To a large degree, of course, you have unless you have a strong leg and foot. On the brighter side, you are not much worse off than you would have been in a large car with no power brakes, such as the Webmaster's 1973 Dart Swinger."
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I'm not sure how to tell if the pump is running or not. I never lost my power assist the months and months the ABS panel light was on. But maybe I have now; I'm not sure though. Should this be the next place I look (at the master cylinder) and if so, what am I getting into replacing the master cylinder myself. It took me all day to do the rear brakes (I'd done the front plenty of times but never the rear. It wouldn't take me that long now that I've done them once.) Any other suggestions would be appreciated.
Sorry for the long post, but I wanted to be sure I was detailed enough.
Skip Richmond, VA