Brake Booster Operating Test

WARNING: This page is about a different car, the 2018 Kia Forte5 and 2018 Kia Forte. However, it is still accessible from the selected car via links, so may be relevant.

For simple checking of the brake booster operation, carry out the following tests.

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 inoperative.

Fig 1: Checking Brake Booster Operation
Courtesy of KIA MOTORS AMERICA, INC.
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 inoperative.

Fig 2: Pressing Brake Pedal (When Engine Start And Stop)
Courtesy of KIA MOTORS AMERICA, INC.
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 inoperative.
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 malfunction.

Fig 3: Checking Valve, Vacuum Hose And Booster For Malfunction
Courtesy of KIA MOTORS AMERICA, INC.