- Slack adjuster
- Service brake control valve
- Service brake
- Brake accumulator unloader valve
When a slack adjuster strokes correctly, a small amount of pressure on the service brake piston will be present after the brakes are released.
The 785G trucks are equipped with a single control valve and mounting that is located below the truck body on the left side. The control valve and mounting is a block with strategically drilled holes. The holes direct oil flow from the brake pump to the service and parking brakes.
The service brakes and the retarder are hydraulically engaged and released with springs. When the service brake or the retarder is applied, oil is sent through the slack adjuster to the service brake and the retarder oil passage.
If pressure is maintained in this passage, the brakes could drag.
Use the purge valve to remove air from the hydraulic system for the service brake and the retarder.
Brake Accumulator Unloader Valve
This valve could be sticking allowing pressure into the brake system. Pressures at the slack adjuster could be enough to cause the brakes to drag. creating excessive heat in the brake cooling system