What does brake servo do?
The brake servo reduces the force you need to apply to the pedal when braking. The negative pressure in the engine’s intake manifold is used to achieve this. Both pneumatic and hydraulic systems exist. In cars with power steering, the servo pump may be used for this purpose.
What do duo servo brakes do?
Duo servo type drum brake Strong pressure from the servo effect (self-boosting effect) of the primary shoe is transmitted to the linked secondary shoe, thus generated a very large braking force. This type is mainly used for parking brakes on passenger cars, the center brakes on trucks, and brakes on forklifts.
How to check a brake servo fault in a car?
Start the engine and leave it running until a steady vacuum registers on the gauge. Switch off the engine and check that the vacuum is maintained for a period of five minutes ( Figure 4 ). Prise out the non-return valve from the servo unit and connect the vacuum tester to the servo side of the valve ( Figure 5 ).
How does the servo work on a rover?
When pressing the brake pedal gently the pressure from your foot is all that is working the brakes. When you press harder the pressure in the slave cylinder opens the air valve and the servo comes into action, using the suction from the engine to apply the pressure.
How is the servo connected to the brake pedal?
Make a sketch of the way the servo pushrod is connected to the brake pedal, and how the vacuum hose is connected to the servo. Disconnect them both. Unbolt the servo unit from its bracket on the bulkhead and withdraw it. If there is a gasket between the servo and the bulkhead, check whether it is worn; renew if necessary.
How can I find out if my servo is working?
To diagnose whether the servo system is working correctly, ZF Aftermarket engineers recommend using a handheld vacuum tester and a structured series of tests as follows. With the engine switched off, press the footbrake repeatedly until the pedal feels firm – this releases any residual vacuum in the system.