The brake master cylinder is a crucial part of the vehicle’s braking system.  It is used to convert the mechanical force from the brake pedal into hydraulic pressure in order to stop the vehicle.  The brake system is split into two circuits and the pressure in each circuit is controlled by the brake master cylinder.

The brake master cylinder consists of two reservoirs for brake fluid and two pistons, and is attached to the brake lines.  When the driver depresses the brake pedal, this pushes on the first piston which causes pressure to build up in the brake master cylinder.  As this pressure builds up it causes the second piston to compress the brake fluid.  This pressure should be even in both cylinders.  If it’s not, it is most likely caused by a leak.  In the case of a leak, the brake master cylinder to operate using one piston.  This will cause the driver to have to press the brake pedal down further and further until eventually the brakes will fail.  Any damage to the brake master cylinder should be minimised and the master cylinder should be repaired immediately.