On Mon, 1 Jul 1996, john peloquin wrote:
> Dear Ray,
>
> How does one tell if this is indeed the problem? It appears I have
> precisely this type of problem- additionally the brake pressure warning
> light goes on too. (1970 MGB-GT)
>
> JOhn Peloquin
>
I'm not sure what a definitive test would be. However, the classic symptom
of a failed seal is that the brake pedal sinks slowly to the floor under
light to moderate pressure. It may or may not sink if you apply hard
pressure (hard pressure can expand the cup seals so they seal
effectively, whereas they may leak under light pressure).
The sinking pedal may be due to fluid leaking past the wheel cylinder
seals. Once it gets past, it will quickly appear in the brake and/or on
the floor. Also, you will find that the master cylinder reservoir needs
frequent replenishment.
The sinking pedal also can be caused by failure of the primary seal of
the master cylinder. In that case, however, the fluid may just goes back
into the reservoir. You may see no leak, and may not have to add fluid.
In a hydraulic clutch system, the pedal normally goes to the floor. The
symptom is that if the pedal is held on the floor the clutch slowly
engages.
Ray Gibbons Dept. of Molecular Physiology & Biophysics
Univ. of Vermont College of Medicine, Burlington, VT
gibbons@northpole.med.uvm.edu (802) 656-8910
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