9-3 Convertible (9400) L4-2.0L Turbo (B205) (2000)
Brake Master Cylinder: Description and Operation
Master Cylinder
Master cylinder
The master cylinder consists of a tandem cylinder manufactured in steel.
As the car has two independent brake circuits, it also has one master cylinder with two independent pressure chambers. There are two pistons in the
cylinder: one primary piston (closest to the brake pedal) and one secondary piston, each with a return spring. The secondary piston has a central valve
of steel that opens a passage to the brake fluid reservoir in rest position.
From the master cylinder, two pipes (primary/secondary) run to the ABS unit (valve block) that, in turn, provides brake fluid to the wheel cylinders
The brake fluid reservoir is mounted directly on the master cylinder.
Rest (brakes off) position
In rest position, the return springs press the pistons to their rear end positions. In this position, both return passages are open and the brake system is
not under pressure. The backward movement is limited by a stop pin.
Brake applied (both circuits operating)