2753436 - 3330DA Check operation of brake servo vacuum circuit and vacuum unit

Discharge the vacuum in the servo unit, with the engine stopped, by pressing and releasing the brake pedal repeatedly and vigorously.With the brake pedal pressed, start the engine without accelerating.Check that after a few seconds, the brake pedal advances in accordance with the increase in pressure brought about by the operation of the servo unit.Release the brake pedal and, without further action, turn off the engine.After about 10 minutes operate the brake pedal, with the engine switched off, and check that when it is pressed for the first time, it lowers with assistance from the servo unit, and that subsequently it gradually becomes harder.