Service function guideBrake Booster and Vacuum Pump Test

This guide covers the complete diagnostic and service procedure for testing brake boosters and vacuum pumps on a wide range of passenger vehicles and light commercial vans. It is written for working mechanics and experienced DIY owners who already understand hydraulic brake fundamentals and want a repeatable method to confirm assist and vacuum supply. You will learn how to prepare the vehicle safely, run engine-on and engine-off assist checks, measure vacuum with a gauge, isolate booster versus pump versus check-valve faults, and interpret the results against factory service information. After finishing, you will be able to decide whether the booster, the vacuum pump, the check valve, or the supply circuit is at fault and document the result for the customer or your own records.