SAAB WIS ONLINE

Vacuum pump

Vacuum pump

To increase the braking effect on Saab 9-5 2.0 and 2.3 with automatic transmission, these cars have been equipped with an additional vacuum pump. The pump provides the brake servo with negative pressure when the engine is unable to supply this fully.

Electrically driven pump


The pump is driven by an electric motor and controlled by a sensor in the intake manifold.

The following conditions must be met before the pump starts:


• Ignition on

• Vacuum less than 0.35 bar (stops at 0.4 bar)


The pump is located in front of the battery. The connection cable has three diodes connected in series to ensure that the pump is fed with the correct voltage, and that the correct pump speed is attained

Mechanically driven pump


The pump is ring type, mounted on the cylinder head and driven by the camshaft. Since it is connected to the camshaft, the speed of the pump is half that of the engine, and negative pressure is produced continually for the brake system.