View single post by Mark Rosenbaum
 Posted: 08-09-2006 02:55 am
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Mark Rosenbaum

Joined: 03-12-2005
Location: Kingman, Arizona USA
Posts: 532
The most likely cause is a defective brake hose with a deteriorated lining that acts as a one-way valve and won't let brake fluid return to the master cylinder.  As an alternative, there might be debris in the caliper's internal passageway performing the same undesired function to one or both pistons.

Given the work you've described in regard to moving the pistons, it seems fairly unlikely that one of these would be sticking.  Still, there's no piston return mechanism other than the wobble of the brake disk and a slight suction when the brake pedal is released, so with suitable rust in place, it's possible for a piston to stick in the 'brakes applied' position.

I agree with you that a defective master cylinder seems very unlikely.