Next time this happens, crack the steel line open at the master cylinder. If the brake releases, suspect the brake fluid is contaminated with petroleum product. That will make the rubber lip seals in the master cylinder expand and grow past the return ports and block them. This will start out affecting one front wheel and the opposite rear one. The clue is the rubber bladder seal under the cap will be ballooned up and mushy.
If the brake does not release at the master cylinder, do you have anti-lock brakes? There could be a problem in the hydraulic controller. Approach that the same way. Crack open the steel line for the left front wheel to see if it releases.
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Thursday, June 2nd, 2011 AT 11:37 PM