Quote:
Originally Posted by T-Cut
I guess you're talking about the Sinking Pedal Phenomenon (SPP) as I call it. This is a well known effect and is broadly regarded as normal behaviour. Some people associate it with flipped seals in the master cylinder, but since it only happens when the engine's running and the car stationary, I believe it's a system control effect. The braking control system involves road speed, wheel speed and pedal pressure to determine what happens with the hydraulic pressure. Under the conditions SPP happens, I believe the fluid is simply recycled in the master cylinder. So, there is no loss or leakeage. If you check the level regularly, you should have nothing to worry about regarding SPP.
You can read the previous discussions on the subject by seaching for "SPP" (include the quotes).
TC
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I wouldn't say 'normal behaviour' . Neither of my cars do it (funnily enough I double checked mine this evening), and nor has any other car I've driven including a few other makes with the same ABS.
I'm also fairly certain that there's no pedal / fluid pressure monitoring on this system. Certainly I've not seen the pressure sensor which is normally screwed into the side of the modulator valve block. I would think it only happens with the engine running because of the extra assistance from the servo.
I'd also point out the OP says he is losing fluid, so I don't think it's SPP anyway.