Siezing brakes: Time to think

[John Larson]

There seems to be some confusion here.  The seizing brake problem is ALWAYS
the master cylinder, except in the rare case of all 4 rubber lines clogging
up or all four slave units (calipers) freezing up at the same time.  It is
NEVER the accumulator, nor is it likely to be the booster.  Although the
"bomb" is better called the "hydraulic accumulator", you must never think
that the term "hydraulic" is the same usage as in "hydraulic" brakes.
Hydraulic brakes are brakes that are actuated by hydraulic fluid moved
throughout tubing by force applied to the system through the master
cylinder, and causing the slave cylinders (be they wheel cylinders or
calipers) to exert pressure on the friction surfaces.  The term "hydraulic
assisted brakes" refers to the system which acts as a force multiplier on
the brake hydraulic system.  There are also vacuum assisted and air pressure
assisted brake systems.  Failure of components in the hydraulic assist
system causes a hard pedal.  Failure of the "bomb" results in a loss of
reserve assist, as when the engine is not running, and may be only slightly
noticeable when driving the car under normal conditions.  Failure of the
pump (or that section of the pump running the brake booster) may result in
no assist even when the car is running.  It CANNOT cause the brakes to
engage or seize, as its force is ABSENT.  In the same vein, the failure of
the bomb CANNOT cause those symptoms, it can only result in a hard
(unassisted) pedal.
Bottom line, you may need a "bomb", and you certainly need a master
cylinder, but they're about as related as the fuel filter and the oil pump.
HTH,  John