To test the booster, how many brake applications should be made with the ignition off?

To successfully test the brake booster, it is essential to make multiple brake applications to ensure that the booster operates properly when there is no power assist from the engine. The correct number of brake applications for this test is generally three or four with the ignition off. This allows the technician to observe how the brake pedal feels and whether it holds pressure, indicating that the booster is functioning as intended. During these applications, the vacuum in the booster is depleted, simulating a condition where the engine is off and not providing any assistance.

If only one or two applications were performed, it may not be sufficient to gauge the booster’s behavior under low vacuum conditions. Similarly, conducting five or more could lead to unnecessary testing and may not be practical. Therefore, three or four applications strike the right balance to verify the effectiveness of the brake booster within the testing parameters.