Checking the performance of the vacuum booster

Press the brake pedal 5-6 times with the engine off to create in cavities A and E (see fig. 117) the same pressure, close to atmospheric pressure. At the same time, the force applied to the pedal determines whether the valve body is stuck.

Keeping the brake pedal depressed, start the engine. With a working vacuum booster, the brake pedal after starting the engine should «go ahead». If this does not happen, check the fastening of the hose tip, the condition and fastening of the tip flange in the amplifier, the hose to the tip and the engine inlet pipe fitting, since loosening or damage to the fastening sharply reduces the vacuum in cavity A and the efficiency of the amplifier.