Checking Service Brake: High and Low Pressure Tests

CAUTION: The high and low-pressure tests (leak check) must be conducted with the engine switched off.


High-pressure Leak Test:
- Perform test on both brake circuits.
- 1st brake circuit, front axle
- 2nd brake circuit, rear axle





- Unscrew bleeder screw, connect pressure tester and bleed.





- Depress brake pedal with specified force, refer to Dimensions, Brakes In General. Specifications
- Hold depressed with a pedal prop.
- After 2 minutes, pressure must not drop by more than 8%.

Low-Pressure Test:
- Perform test on both brake circuits.
- Reset pedal support until test pressure in brake system is equivalent to 2 ... 5 bar.
- Vehicle and tester must remain still as motion would cause incorrect test results.





- Pressure should remain constant during five-minute test.
- Check all rubber parts in case of excessive pressure drop.
- Bleed brake calipers and wheel brake cylinders after finishing test.