This is an interesting problem. The fact that only the front brakes are
affected is probably a clue - clearly there is a one - way valve effect
somewhere in the front system. Assuming that the rear brake system is OK (no
obstruction to the rear brakes), the symptoms suggest that the defect is either
in the front hydraulic system - before it bifurcates to the individual brakes or
in the master cylinder. You probably have a dual piston MC. If I remember
correctly, the two pistons are connected by a link pin. If this breaks, the
secondary piston may not be pulled back by the spring, maintaining pressure in
that part of the circuit (developed the first time you pumped the pedal). If
this were the case I would expect that after an initial gush, no more fluid
could be bled from the front calipers. One potential flaw in this reasoning is
that I am not sure whether the primary and secondary pistons supply only front
or rear brakes. My theory would work if the front piston supplied the front -
don't know off hand - but will check my Midget.
You could localize the problem by disconnecting one line at a time from the
MC. If the problem is as I described the calipers should unlock after you undid
the front line where it goes into the MC. If they remain locked after both are
disconnected, the problem is in the lines - probably at the brake pressure
warning cylinder. It seems unlikely that the problem could be in the calipers
as both would have to be affected.
Please let us know how it turns out.
Tom Wannenburg
74 Midget
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