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Unfortunately, yes Posted by Ari [Email]  (#2847) [Profile/Gallery]
(more from Ari) on Thu, 23 Dec 2004 20:25:12
In Reply to: Brake fluid light with ABS light, Kevin A, Thu, 23 Dec 2004 19:44:28 Members do not see ads below this line. - Help Keep This Site Online - Signup |
You get both the ABS and Brake Fluid lights on at the same time if the ABS pressure is too low.
Background - ABS pressure is used for both ABS and brake boost (depending on year of car, but I'm guessing you've got like a '88-93), When the ABS pressure is below 140 bar, the ABS pump runs, and stops when the pressure hits 180 bar. If the pressure is 100 bar or less, you get both the ABS and Brake Fluid lights.
the pressure is stored in the accumulator, the sphere on top of the brake master cylinder. Every time you hit the brake, you use up some of that pressure for brake boost. When the pressure drops to 140 bar, the pump runs. If the pump doesn't run, the pressure will keep dropping. There is also a little leak-down, even if you don't press the brake pedal.
At 100 bar, you've got about 5 or so hard brake presses left of pressure. Low enough pressure, and you lose brake boost, and you get the hard pedal and long stopping distances.
When the car is off and has been sitting overnight, the pressure in the accumulator leaks down. This fluid goes back into the reservoir. So you should see the brake fluid leve ABOVE the FULL line. Start the car, and you should hear the ABS pump run, and the level drop down to the FULL line,. Hit the brakes a bunch of times, and the level will rise up a bit.
I think you've got two problems going on here, both with the ABS system. The ABS light all by itself implies the ABS has detected a problem during self-test. The fact that the Brake Fluid light has gone out implies that the ABS pump does run. If I had to guess, there is a problem with one of the valves in the ABS system, and that's what the ABS self-test is catching. The valve causes the pressure to leak down fast, so the ABS pump is running almost all the time. It's not designed for that, so it overheats and shuts itself off. Things leak down, and the BF light comes on,
When I say leak down, I'm saying that the fluid stored in the accumulator leaks through valves and back into the reservoir. You don't leak fluid out of the system.
Again, that's just a guess. You could have a pressure switch problem, or a leaky brake master cylinder. And there is a remote chance that you have two separate ABS problems - a bad wheel speed sensor AND an ABS pump problem - not related, but would give you the same symptoms.
You'll really need the ABS codes. Usually a bad ABS pump by itself won't give you an ABS light all by itself.
Next time, please give the year and model of the car - there are year-to-year differences in lots of systems.
posted by 12.76.15...
, Thu, 23 Dec 2004 22:18:02, Thu, 23 Dec 2004 20:25:12 <-- Viewing This Message
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