Brake master cylinder - with oil reservoir function
The master brake cylinder (also known as the brake main cylinder) is the core component of the vehicle's braking system. Its main function is to convert the mechanical force applied by the driver on the brake pedal into hydraulic pressure, and then transfer this pressure through the brake lines to the individual wheel booster units, thereby pushing the brake pads to clamp the brake discs (or brake shoe pads to open), achieving vehicle deceleration or stopping.
The master brake cylinder is usually integrated or closely connected with a brake oil tank (also known as the braking fluid reservoir), and together they form a complete hydraulic braking unit.
The functions of the master brake cylinder
Pressure conversion: When the driver steps on the brake pedal, the pedal pushes the push rod to move the piston inside the master brake cylinder forward.
Hydraulic generation: As the piston moves forward, it closes the oil chamber in front of it, causing the pressure of the brake fluid in the chamber to increase sharply.
Pressure transmission: The high-pressure brake fluid is transmitted through the brake lines to the four wheel booster units (or called wheel cylinders), driving the piston of the wheel cylinder to work, and ultimately causing the brake pads to generate friction with the brake discs, achieving braking.
The function of the brake oil tank
The brake oil tank is a supporting component of the master brake cylinder, and its main function is to store brake fluid and provide a stable and sufficient supply of oil to the master brake cylinder. Its specific functions include:
Oil storage: As the "reservoir" of brake fluid, it ensures that there is always sufficient brake fluid in the system.
Oil compensation: When the brake pads wear out and the piston stroke increases, the oil in the tank will automatically replenish to the master cylinder and wheel cylinders to maintain system pressure.
Maintaining pressure balance: The oil tank cover has ventilation holes and rubber pads, which prevent the formation of vacuum negative pressure or positive pressure in the tank due to the rise and fall of the oil level (when braking or releasing the brake), ensuring that the brake fluid can flow smoothly and without obstruction into the master cylinder, ensuring the sensitivity and consistency of the braking response.
Level indication: The wall of the brake oil tank usually has "MAX" (maximum) and "MIN" (minimum) scale lines. When the brake pads are severely worn, the piston stroke increases, consuming more oil, causing the oil level in the tank to drop. When the level drops near the "MIN" line, it indicates that it is time to check or replace the brake pads.
Anti-pollution: The cover of the brake oil tank can effectively prevent dust, moisture, and other impurities from entering the brake fluid system, avoiding contamination of the fluid and corrosion of the pipes.
In summary, the master brake cylinder is the "heart" of the braking system, responsible for generating and transmitting braking force; while the brake oil tank is its "blood supply system", ensuring that the master cylinder can work continuously and stably. Both are indispensable and jointly ensure the braking safety of the vehicle.
Master brake cylinder (with oil tank) is the core component of the vehicle's braking system, responsible for amplifying the force applied by the driver on the brake pedal and transmitting it to the wheel booster units, thereby achieving vehicle deceleration or stopping. If the master brake cylinder is damaged, it will directly lead to a decline in braking performance and pose a serious safety hazard.
Common manifestations of master brake cylinder failure
When the master brake cylinder fails, the following symptoms may occur:
Brake pedal becomes soft or feels unresponsive when stepped on: When stepping on the brake, it feels soft and lacks elasticity, or the braking effect is still poor even when the pedal is fully depressed, which may be due to the failure of the internal seal of the master brake cylinder causing brake fluid leakage or insufficient pressure.
Brake drift or shaking: The vehicle shows obvious deviation in the braking trajectory, or the steering wheel shakes, which may be related to the uneven pressure distribution of the master brake cylinder or faults in related components (such as the wheel cylinders).
Abnormal noise or non-return of the brake pedal: Abnormal noise occurs when braking, or the brake pedal cannot return to its normal position when released, indicating that the internal mechanism of the master brake cylinder may be stuck or damaged.
Increased braking distance or sudden failure: The braking performance significantly decreases, requiring a longer distance to stop, and in extreme cases, complete failure may occur. Oil leakage phenomenon: Check the connection point between the brake master cylinder and the vacuum booster or the limit screw. If you find brake fluid leakage, it is a typical sign of a malfunction in the master cylinder.
Causes of brake master cylinder damage
Common causes include:
Sealing components aging or wear: Over time, the wear-resistant parts such as the rubber cups and sealing rings inside the master cylinder will age, leading to brake fluid leakage.
Excessive moisture in brake fluid: Brake fluid is prone to absorbing water. When the moisture content exceeds 3%, it will lower the boiling point and corrode internal parts, and regular replacement is required.
Quality issues or improper maintenance: Using inferior parts, not timely maintenance, or air mixed into the braking system can all accelerate the damage of the master cylinder.
Precautions for replacing the brake master cylinder
Timely repair: Once the above fault signs occur, stop driving immediately and contact professional maintenance personnel for inspection to avoid accidents.
Select matching parts: The brake master cylinder must be precisely matched with the vehicle model. It is recommended to choose original factory parts or reliable quality parts when replacing.
Professional installation and exhaust: After replacement, the braking system must be purged to ensure no air remains, otherwise it will affect the braking effect.
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