Residual pressure test
WARNING: This page does not describe the selected car, but rather 17 other vehicles, including the 2009 Audi S4, 2009 Audi A4, 2008 Audi S4, 2008 Audi RS 4, and 2008 Audi A4. However, it is still accessible from the selected car via links, so may be relevant.
Special tools, testers and auxiliary items required
- Brake pressure gauge 0-250 bar V.A.G 1310A
Make sure adequate brake booster pressure for this test.
Before starting:
- Vehicle raised on a two-column hoist.
Make sure that the brake system (master cylinder, brake hoses, brake lines and brake calipers) works properly and is free of leaks.
- Connect Brake pressure gauge 0-250 bar V.A.G 1310A.
Troubleshooting procedure if pads are worn on one side of the vehicle:
- Remove bleeder screw at one of the front brake calipers. Connect pressure gauge (brake pressure gauge 0-250 bar V.A.G 1310A).
- Start engine.
Simulate brake applications at various pressures up to approx. 100 bar.
- Operate brake pedal slowly at various pressures.
- Operate brake pedal rapidly at various pressures.
- Firmly depress brake pedal once as far as it will go.
If wheel is difficult to turn and there is no residual pressure in the system:
- The pad may be sticking in guide rail in caliper, or caliper may be dirty.
- The piston may be seized or sticking in caliper.
If wheel is difficult to turn and there is residual pressure in the system:
- The pedal mechanism may be sticking, or foreign bodies in pedal mechanism.
- If it is possible to pull back the brake pedal slightly so that the brake pressure drops to zero, the brake booster must be replaced, or the pedal mechanism is sticking.
Checking brake master cylinder
- Connect brake pressure gauge 0-250 bar V.A.G 1310A and build up a pressure of 5 - 10 bar without vacuum. Replace brake master cylinder if pedal yields continuously under this pressure.