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Re: Brake Loss 9000 Aero Posted by Ari [Email]  (#2847) [Profile/Gallery]
(more from Ari) on Mon, 3 Dec 2007 09:00:43
In Reply to: Brake Loss 9000 Aero, Tim Dunne, Mon, 3 Dec 2007 07:10:26 Members do not see ads below this line. - Help Keep This Site Online - Signup |
I'm assuming you have a '94 or earlier car.
The ABS pump provides pressure for both ABS and Brake Boost. If the ABS pressure is too low, BOTH the ABS and Brake Fluid lights are on. Without that pressure, there is no brake boost - this is worse than not having power brakes - you can stop, but it'll take lots of force and still not be very effective, as you well know.
The ABS pump pumps fluid from the reservoir (where you fill it) into the accumulator - the black sphere - that stores the pressure. So as the pump runs, the level in the reservoir drops. So after sitting a while, the level should actually be well ABOVE the FULL line. It drops to the FULL line after the pump has stopped running.
It is normal for the ABS pressure to be low after the car has been sitting - the lights can be on for 15-45 SECONDS or so. 10-15 minutes is not a good thing.
The first question - what is the fluid level before starting the car? What is it after the lights have gone out? It should be at the FULL level when the lights have gone out.
Second question - when was the last time you had the brakes bled? Excess air in the system can cause major problems. And if the fluid level has dropped too low, it can let in air.
OK, assuming the fluid levels are OK and there isn't any air in the system, when you first start the car, does the ABS pump start running immediately? You should hear the hum from the master cylinder area, and see the fluid level dropping. If it isn't starting immediately, but instead takes 10 or 15 minutes to start running, I'd suspect the ABS pump relay contacts are bad, or a bad pump. Hope for the relay.
If the pump starts running but the level drops very slowly, if at all, it may be a bad pump, or a very leaky master cylinder (internal leak). Not much to do here but replace them at a major cost. This could also be due to lots of air in the system.
If the level drops quickly, but the pump doesn't shut off and keeps running for 10 minutes, it might be a bad high pressure switch. THis is the switch that tells the pump to stop running when the pressure is high enough.
But first questions-
Year of car?
Brake fluid levels right?
Brakes bled / fluid replaced recently?
posted by 192.249....
, Mon, 3 Dec 2007 09:00:43 <-- Viewing This Message, Tue, 4 Dec 2007 17:35:29
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