Front Slack Adjuster
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| Illustration 1 | g02315073 |
Location of the front slack adjuster | |
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| Illustration 2 | g01261679 |
Components of the front slack adjuster (1) Outlet to a front service brake (2) Piston (3) Inlet from the Brake Valve (Front Service Brake) (4) Piston (5) Outlet to a front service brake (6) Oil chamber (7) Oil passage (8) Small piston (9) Small piston (10) Oil passage (11) Oil chamber (12) Passage for makeup oil (13) Passage for makeup oil | |
The front slack adjuster is located between the Brake Valve (Front Service Brake) and the front service brakes. When the Foot Brake Control (Service) is used or when the retarder is used, the Brake ECM sends current to the front service brake solenoid. When the front service brake solenoid is energized, Brake Valve (Front Service Brake) then sends oil to inlet (3) and into the front slack adjuster. The oil pressure in the front slack adjuster pushes pistons (2) and (4) away from the center of the slack adjuster. Pistons (2) and (4) push the oil in oil chambers (6) and (11) through outlets (1) and (5) to the front service brakes in each wheel. This oil initiates the front service brake application.
If the brakes have worn, the oil from chambers (6) and (11) may not complete the front service brake application. When pistons (2) and (4) are against the ends of the front slack adjuster, the oil from the Brake Valve (Front Service Brake) will fill oil passages (7) and (10) . If the pressure in passages (7) and (10) is higher than the pressure in outlets (1) and (5) , small pistons (8) and (9) move away from the piston seats. Additional oil from the Brake Valve (Front Service Brake) can flow through the open piston seats to passages (12) and (13) . This oil flows through outlets (1) and (5) in order to complete the front service brake application.
When you stop applying the front service brakes, the Brake ECM stops sending current to the front service brake solenoid. When the front service brake solenoid is deenergized, the Brake Valve (Front Service Brake) will not send oil to the front slack adjuster. The lower pressure in outlets (1) and (5) will cause small pistons (8) and (9) to return to the piston seats. Small pistons (8) and (9) will block passages (12) and (13) . When oil stops filling the front service brakes, the return springs in the brakes will push the service brake pistons. The service brake pistons push the oil from the brake application back into outlets (1) and (5) of the slack adjuster. This oil pushes pistons (2) and (4) to the center of the slack adjuster. The front service brake is released completely.
Rear Slack Adjusters
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| Illustration 3 | g02315074 |
Location of the rear slack adjusters | |
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| Illustration 4 | g03642125 |
Components of the rear slack adjuster (1) Inlet from Brake Valve (Rear Service, Retarder Control, Traction Control) (2) Piston (3) Outlet to a rear service brake (4) Oil chamber (5) Small piston (6) Oil passage (7) Passage for makeup oil | |
The rear slack adjusters are located between the Brake Valve (Rear Service, Retarder Control, Traction Control) and the rear service brakes. When the Foot Brake Control (Service) is used or when the retarder is used, oil from the Service Brake Valve (Foot Control) flows to the Brake Valve (Rear Service, Retarder Control, Traction Control). The Brake Valve (Rear Service, Retarder Control, Traction Control) then sends oil to inlet (1) and into the slack adjusters. The oil pressure in the rear slack adjusters pushes pistons (2) towards outlet (3) . Pistons (2) push the oil in oil chamber (4) through outlet (3) to the rear service brakes in each wheel. This oil initiates the rear service brake application.
If the brakes have worn, the oil from chamber (4) may not complete the rear service brake application. When piston (2) is against the ends of the rear slack adjusters, the oil from the Brake Valve (Rear Service, Retarder Control, Traction Control) will fill oil passage (6) . If the pressure in passage (6) is higher than the pressure in outlet (3) , small piston (5) move away from the piston seats. Additional oil from the Brake Valve (Rear Service, Retarder Control, Traction Control) can flow through the open piston seats to passage (7) . This oil flows through outlet (3) in order to complete the rear service brake application.
When you stop applying the rear service brakes, the Service Brake Valve (Foot Control) will stop sending oil flow to the Brake Valve (Rear Service, Retarder Control, Traction Control). The Brake Valve (Rear Service, Retarder Control, Traction Control) then stops sending oil to the rear slack adjusters. The lower pressure in outlet (3) will cause small piston (5) to return to the piston seats. Small piston (5) will block passage (7) . When oil stops filling the rear service brakes, the return springs in the brakes will push the service brake pistons. The service brake pistons push the oil from the rear service brake application back into outlet (3) of the rear slack adjusters. This oil pushes pistons (2) towards inlet (1) . The rear service brake is released completely.