A pushrod drives the primary piston to compress the brake fluid in its circuit.
As the primary piston moves, hydraulic pressure builds inside the cylinder and brake lines.
This pressure drives the secondary piston to compress the brake fluid in its circuit.
Brake fluid moves through the brake lines, engaging the braking mechanism
Brake master cylinder
Rear brake master cylinder
When you press down on the brake pedal, that force pushes a piston through the brake cylinder, converting the force into hydraulic pressure.
This pressure pumps hydraulic fluid through the brake lines, transmitting pressure to a secondary cylinder at each wheel’s braking mechanism.
The secondary cylinders drive the caliper piston to engage the brake calipers in disc brakes (the wheel cylinder in drum brakes). This action then goes on to stop the wheel.
When does we should replace the brake master cylinder?
Abnormal brake pedal behavior
Contaminated brake fluid
Pull brake hand and vehicle did not decrease speed.