For 1990-2009 cars

1. Apply the parking brake and block the vehicle wheels.
2. Start the engine and charge the system to the air compressor governor cut-out point.
3. Turn off the engine.
4. Drain the air pressure from the supply reservoir. Refer to Draining Reservoirs .

Important: Applying the brakes repeatedly drains the supply air reservoir pressure. This may cause the brakes to appear sluggish.

5. Have an assistant apply and release the brake pedal two times.
6. Verify that the front and rear slack adjusters move smoothly and promptly.

• | If the front brakes are sluggish or fail to move, overhaul or replace the single check valve at the front service air reservoir. Refer to Reservoir Check Valve Replacement or Air Brake System Description and Operation .

• | If the rear brakes are sluggish or fail to move, overhaul or replace the single check valve at the rear service air reservoir. Refer to Reservoir Check Valve Replacement or Air Brake System Description and Operation .

7. Start the engine.
8. Charge the system air pressure to the governor cut-out point.
9. Stop the engine.
10. Remove the wheel blocks.