>There must be an air bubble somewhere!
Perhaps, but you may want to take a look at the wheel or master cylinders.
Pedal action simply forces hydraulic fluid through the system to the wheel
cylinders which react by transmitting the hydraulic pressure outward to the
brake pads/shoes.
If the seal between the cylinder walls and the rubber cup is imperfect, or
the rubber cup itself is perforated, pedal pressure - slowly applied - will
allow hydraulic fluid to escape around the cylinder piston. If the leak is
to the inside (past the master cylinder primary piston, for example) the
result will be a gradual loss of pedal with no external leak. All would
return to normal as the fluid leaked back again. Quick depression of the
pedal in normal braking would be sudden enough to not allow enough fluid to
leak by to cause a loss of braking power.
If the system were bled twice, I doubt there would be enough air left in the
system to cause this problem. Besides, the pedal would be soft all the time,
not just under slow gentle pedal pressure.
Look for bad internal cylinder rubber parts!
I hope this helps.
Regards,
Lew Palmer
lew@uci.com
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