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How about the ABS light? Posted by Ari [Email] ![]() ![]() In Reply to: BRAKE FLUID LIGHT, JLD900S, Tue, 1 Mar 2005 13:28:39 Members do not see ads below this line. - Help Keep This Site Online - Signup |
If you turn the ignition key to ON, but don't start the car, you should get a bunch of dash lights. One should be the ABS light. If it doesn't come on, then the ABS light is burned out/loose.
Typically when you start the car after it has been sitting a while (like overnight), the ABS and Brake Fluid lights will come on for a few seconds, then the Brake Fluid light wink out, followed by the ABS light.
The ABS system uses pressurized brake fluid for the ABS, AND for brake boost. It pumps the fluid into an accumulator, the sphere sitting on top of the brake master cylinder. The accumulator has a diaphram in the middle, with nitrogen gas on one side, brake fluid on the other. When the system pressurizes, it pumps fluid into one side, compressing the gas. This provides pressure for the system. Think of it as a water balloon - you can put water in, and the balloon expands - open it up, and the contraction of the rubber pushes the water out.
If the ABS and Brake fluid lights come on, it means that the ABS pressure is low. A common failure is for the diaphram in the accumulator to leak. Now, the sphere fills with brake fluid. Since fluids don't compress, you can get pressure, but no force. So the second you hit the brake pedal, the pressure drops, and the light comes on.
Simple test - start the car, and wait about 1 minute. You should hear the ABS pump shut off. Now, hit the brake pedal hard and fast. Count the number of pedal presses before the lights come on. It should be on the order of 12 to 15 before the lights come on. If it comes on after 5 pulses, the accumulator is probably shot. Since it's coming on after one, that's a pretty sure sign that the accumulator is shot.
check the archives, even over on the 9000 board, on replacing the accumulator. It's no big deal, but you do need to bleed thepressure down first.
posted by 12.76.15...
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