Run the engine for one or two minutes, and then stop it. If the pedal depresses fully the first time but gradually becomes higher when depressed succeeding times, the booster is operating properly, if the pedal height remains unchanged, the booster is defective.

With the engine stopped, step on the brake pedal several times.

Then step on the brake pedal and start the engine. If the pedal moves downward slightly, the booster is in good condition. If there is no change, the booster is defective.

With the engine running, step on the brake pedal and then stop the engine.

Hold the pedal depressed for 30 seconds. If the pedal height does not change, the booster is in good condition, if the pedal rises, the booster is defective.

If the above three tests are okay, the booster performance can be determined as good.

Even if one of the above three tests is not okay, check the check valve, vacuum hose and booster for defect.

Disconnect the brake booster vacuum hose (check valve built in) (A) at the booster (B).

Start the engine and let it idle. There should be vacuum available. If no vacuum is available, the check valve is not working properly. Replace the brake booster vacuum hose and check valve and retest.

Block the tire with a suitable block.

Relese the parking brake and check the brake fluid level.

With the engine stopped, step on the brake pedal more then 20 times.

When IG ON, check whether parking brake pedal waring lamp turn on.

If the parking brake waring lamp is not off, stop the engine, and step on the brake pedal more than 20 times.

Check the continuity between terminals of the vacuum switch, after disconnenting the connector from the vacuum switch.

If there is no continuity, replace vacuun switch.