Checking the operation of the brake booster check valve (Mitsubishi Lancer 9)

Contents: Table. Checking the vacuum booster…⤓ Checking the operation of the brake…⤓ Brake fluid pressure with brake…⤓ Brake fluid pressure with brake…⤓ Brake fluid pressure with brake…⤓ Brake fluid pressure with the brake…⤓

Caution: When testing the check valve, it must be connected to a vacuum hose.

1. Remove the vacuum hose.

Note: When removing the vacuum hose, do not disconnect the check valve from it.

2. Check the operation of the check valve using a hand vacuum pump according to the table below.

Table. Checking the vacuum booster check valve.

Connecting the vacuum pump	Admission/rejection criteria
From the brake booster side (1)	A vacuum is created and maintained
From the intake manifold side (2)	No vacuum is created

Note: If the check valve is faulty, it must be replaced together with the vacuum hose.

Checking the operation of the brake booster using pressure gauges

1. Connect the pressure gauges and vacuum gauge as shown in the figure.

2. Perform a no-load amplifier test.

Start the engine. Stop the engine when the vacuum is 67 kPa. After stopping the engine, the vacuum does not drop within 15 seconds.

3. Perform a load test of the amplifier.

Start the engine and press the brake pedal with a force of 200 N. Stop the engine when the vacuum is 67 kPa. After the engine stops, the vacuum will decrease to approximately 3.3 kPa.

4. Perform the test with the vacuum booster not working.

Stop the engine. Make sure the vacuum is 0 kPa. Make sure the brake fluid pressure corresponds to the maximum permissible values with a brake pedal force of 100 N and 300 N.

Brake fluid pressure with brake booster not working (sedan).

Brake pedal force, N	Brake fluid pressure, kPa
100	0
300	1824

Brake fluid pressure with brake booster not working (station wagon).

Brake pedal force, N	Brake fluid pressure, kPa
100	0
300	1582

5. Perform a test of the amplifier operation.

Start the engine. When the vacuum reaches 67 kPa, make sure that the brake fluid pressure corresponds to the maximum permissible values with a brake pedal force of 100 N and 300 N.