The master brake cylinder (MBC) is a key element of the brake system of any car. It is what provides pressure in the brake lines, transmitting force from the pedal to the wheels. Malfunctions in its operation can lead to complete or partial loss of brakes. Therefore, it is important to know how to check the master brake cylinder, especially if you have a car like VAZ 2106, VAZ 2101, GAZelle, Passat B3 or Lanos, where diagnostics can be done by yourself.

When should you check the master brake cylinder

The first signs indicating a possible malfunction of the MBC:
  • The brake pedal "sinks" when pressed;
  • The car brakes poorly, especially with repeated presses;
  • Brake fluid leak in the area of the cylinder;
  • The car pulls to the side when braking;
  • An unusual sound or squeak appeared when pressing the pedal.
If you notice at least one of these symptoms, it's time to learn how to check the master brake cylinder on your car.

How to check the master brake cylinder without removal

Here is a basic step-by-step instruction suitable for most models: VAZ 2106, VAZ 2101, GAZelle, Lanos, VAZ 2110, Passat B3.

1. Checking the brake pedal

  • Turn off the engine.
  • Press the brake pedal several times.
  • If the pedal becomes "hard" and then starts to slowly sink down, this is a sign of pressure leakage inside the MBC.
Important: with a working cylinder, the pedal remains motionless under pressure.

2. Inspecting the brake fluid

  • Open the brake fluid reservoir.
  • Make sure the level is between the "MIN" and "MAX" marks.
  • Check for leaks on the surface of the cylinder, especially in the area of connections with the tubes.

3. Checking for leaks

  • Ask an assistant to press the brake and hold the pedal.
  • Meanwhile, check the cylinder and connections for leaks.
  • If fluid is squeezed out - the seal is broken, the cylinder requires replacement or repair.

4. Diagnostics with the engine running

  • Start the engine.
  • Slowly press the brake pedal.
  • With a working cylinder, the pedal will be "springy".
  • If it is soft or sharply sinks, the master brake cylinder is most likely faulty.

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Features of checking on different models

How to check the master brake cylinder VAZ 2106 and VAZ 2101

The classic "Zhiguli" are distinguished by a simple design, which simplifies diagnostics.
  • These models often have internal leakage between circuits.
  • The check is similar to the general scheme, but additionally you can disconnect the brake tubes and alternately plug the outlets to determine the circuit with the leak.

How to check the master brake cylinder Lanos

  • In Lanos, piston seals often wear out, especially with poor quality fluid.
  • Inspect the vacuum booster for traces of brake fluid - if present, the MBC is leaking inside.

How to check the master brake cylinder VAZ 2110

  • In the "desyatka", the master cylinder is sensitive to wear of rubber parts during temperature changes.
  • Feature: if with the engine running the pedal becomes "spongy", it means there is internal wear of the MBC, despite the absence of external leaks.

How to check the master brake cylinder GAZelle

  • GAZelle is often used under increased loads, and the MBC can fail faster.
  • Pay attention to fogging of the rear part of the cylinder and booster.
  • Also, remove the protective dust cover and check for fluid under it.

How to check the master brake cylinder Passat B3

  • On Passat, problems with vacuum often occur, which externally resembles a MBC malfunction.
  • If after diagnostics no leaks are detected, also check the operation of the brake booster and vacuum hoses.

What to do if the master cylinder is faulty

If after all checks you are convinced that the master brake cylinder is faulty, it is best to:
  • Not delay replacement - the brake system is responsible for safety.
  • Buy a quality analogue or original part.
  • Be sure to replace the brake fluid after installing a new MBC.
  • Bleed the brake system.
Knowing how to check the master brake cylinder should be known by every car owner, especially when it comes to cars with a simple design - such as VAZ 2106, VAZ 2101, GAZelle, Lanos or Passat B3. Regular diagnostics will help prevent an emergency on the road. If in doubt - it is better to trust specialists.