9-3 (9440) V6-2.8L Turbo (2008)
/v6-2.8l_turbo/Page-2486001.png)
Vacuum Pump: Description and Operation
Vacuum Pump
To secure the supply of vacuum in the brake servo unit under varying operating conditions, there is a vacuum pump fitted in the car. This pump
supplies the brake servo unit with negative pressure when the engine is not able to provide a sufficient vacuum.
Brake Vacuum Circuit
In a situation with an idling engine and a stationary car, the brake pedal may feel "soft" and sink somewhat lower than normal when applied. This is
completely normal and will not affect braking force in a negative manner.
Cars equipped with HFV6 are fitted with an electric vacuum pump and two connections to the intake manifold. One of them has a venturi for
amplifying the brake vacuum.
The electric pump is powered by +30 voltage via a relay. The relay in turn is governed by a pressure sensor located on the hose between the vacuum
pump and the brake servo. This sensor comprises a diaphragm, spring, switch and check valve. The switch closes to start the pump at a pressure of 49
±3 KPa. When the pressure reaches 42 ±3 Kpa, the switch will open and the pump will stop.
On the vacuum pipe between the electric vacuum pump and the brake servo unit is a T-coupling. From this T-coupling, the pipe returns to the intake
manifold where it divides to two connections. On one of the pipes, connected directly to the intake manifold, there is also a check valve.
