Testing the master cylinder

Testing the master cylinder comes down to visually inspecting the leak and maintaining the brake pressure. The master brake cylinder is the first element of the hydraulic system where it creates brake pressure and transmits the brake fluid thrust to the brake units on the vehicle wheels. When the brake pedal sinks, the lower brake fluid level in the reservoir, the brake warning lamp illuminates, or the brake pedal reserve height is too low, check the master cylinder for external and internal leaks.

The external leak test includes an inspection of the brake fluid levels in the reservoir and a visual inspection of the brake cylinder for obvious signs of leakage. Then check all brake line fittings on the brake cylinder, sensor connections, tank seals, and the rear of the master cylinder near a vacuum brake booster. Also, the inside of the vacuum hose on a vacuum brake booster is checked for the presence of brake fluid, which means that the brake fluid passes next to the primary piston in the master brake cylinder and the front seal of a vacuum brake booster.

After a visual inspection of the external leak, check that the brake pressure is maintained. Start the engine and gently pressed the brake pedal. The pedal should hold the same position without falling for at least 1 minute. If the pedal sink, it is a sign that there is an external or internal leak in the hydraulic brake system and requires a further testing system.

If the brake pedal sink during the stable position test and the brake pedal pressure is tested, check the master cylinder for internal leakage. Remove the tank cap and observe the brake fluid level. When the brake pedal is depressed and released, a change in level should occur. However, if the brake fluid level rises when the pedal is depressed, the master cylinder may have an internal leak.

We check the existence of an internal leak using the blocked cylinder method. The brake hoses are removed from the cylinder. Bleeding the master brake cylinder and locks (plugs) are installed on the cylinder connections of the removed hoses. Slowly depress the brake pedal and hold it firmly. Check that there are no leaks on the blocked plugs. If the brake pedal sink, there is an internal leak in the master cylinder.

To testing the master cylinder, follow these steps:

Checking the external leak

Check the brake fluid level in the reservoir. Visually inspect the master cylinder for leaks: brake line connections, sensors, tank seals, and rear to a vacuum brake booster. Check the inside of the vacuum hose for brake fluid.

Checking the maintenance of brake pressure

Start the engine, depress the brake pedal, and keep it depressed for 1 minute. If the pedal sink, there is an external or internal leak in the hydraulic brake system.

Checking the internal leakage

Depress the brake pedal and observe the brake fluid level in the reservoir. If the brake fluid level rises, there is a possibility that the master cylinder has an internal leak.

Checking by the method of blocking

Remove all brake hoses from the master cylinder. Bleeding from the cylinder and insert the plugs in the places of the removed hoses. Depress the brake pedal and hold firmly. Check for fluid leaks on the plugs. If the brake pedal sink, there is an internal leak in the master cylinder.