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| Illustration 1 | g01067564 |
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(2) Air tank check valve
(4) Primary air tank (5) Starter relay valve (10) Starter solenoid valve (11) Air starting motor (14) Air compressor with air compressor governor (15) Air dryer with an air relief valve (16) External air supply (22) Air suspension seat (23) Solenoid valve for autolube (24) Air system pressure protection valve (26) Air suspension buddy seat that is an attachment (27) Cleanout hose that is an attachment (28) Air horn solenoid (32) Secondary air tank (33) Parking brake reset valve (A) Brake air pressure sensor | |
Note: The darkened lines show air pressure and the arrows show the direction of flow.
If the pressure in primary air tank (4) is above the cut-in pressure of the air system pressure protection valve (24), air will flow through pressure protection valve (24). If the pressure in primary air tank (4) is below the cut-in pressure of the air system pressure protection valve (24), you will need to charge the system with an external air supply (16). System air pressure is monitored by brake air pressure sensor (A). Some of the air that flows through air system pressure protection valve (24) supplies starter solenoid valve (10). When the keyswitch is turned to the START position, starter solenoid valve (10) is electrically opened. When starter solenoid valve (10) is open, air from pressure protection valve (24) will flow into air starting motor (11). The air flow pneumatically engages the starter pinion with the engine flywheel ring gear.
When the starter pinion is engaged, internal passages allow air to flow from starter solenoid valve (10) to the control passage of starter relay valve (5). This air flow causes starter relay valve (5) to open. Air now flows from primary air tank (4) to air starting motor (11). Air starting motor (11) will crank the engine.
When the engine is started and the keyswitch is released from the START position, starter solenoid valve (10) closes. The flow of air to the starter pinion is stopped. The gear is disengaged by a spring. This also stops air flow to the control passage of starter relay valve (5). Starter relay valve (5) closes. Air starting motor (11) disengages.
The engine drives the air compressor. When the engine is started, the air pressure from the air compressor will build up until the air pressure reaches the cut-in pressure of the air compressor governor. Then, air flow from the air compressor will flow to air dryer (15). The air flows from air dryer (15) to one-way check valve (2) and into primary air tank (4). When the pressure in the system is above the cut-in pressure of the air system pressure protection valve, pressure protection valve (24) will be open. Pressure protection valve (24) must be open to supply air to starter solenoid valve (10), air suspension seat (22), machine autolube solenoid (23), air suspension buddy seat (26), cleanout hose (27), air horn solenoid (28), secondary air tank (32), and the wastegate for the engine. When the air pressure in all the air tanks reaches the cutout pressure of the air compressor governor, the flow of air into the system will be stopped. When the pressure falls to the cut-in pressure of the air compressor governor, air will flow through the air dryers to the rest of the system. If the pressure in the system drops below
The Parking Brake Reset Valve Is Open
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| Illustration 2 | g01067607 |
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The engine is operating. The parking brake reset valve is open. The air control valve for the parking brake is in the ON position. The secondary brake air control valve is in the OFF position. (B) Secondary brake and parking brake switch (18) Parking and secondary brake valve (30) Secondary brake air control valve (31) Air control valve for the parking brake (32) Secondary air tank (33) Parking brake reset valve (35) Secondary brake inverter valve | |
Note: The darkened lines show air pressure and the arrows show the direction of flow.
Note: Secondary brake and parking brake pressure switch (B) is activated when air control valve (31) for the parking brake is in the ON position and parking brake reset valve (33) is closed.
Air pressure from secondary air tank (32) flows to the secondary brake air control valve (30) and the parking brake reset valve (33). With secondary brake air control valve (30) in the OFF position, air pressure from the secondary air tank (32) would be able to flow to the secondary brake inverter valve (35) and the air control valve (31) for the parking brake. In this case, parking brake reset valve (33) is open and the air pressure from the secondary air tank (32) is stopped at the parking brake reset valve (33).
When parking brake reset valve (33) is in the open position, parking brake reset valve (33) stops the flow of air to parking and secondary brake valve (18). The parking brakes are applied by springs and the parking brakes are released by pressure. When the air flow to parking and secondary brake valve (18) is blocked, the oil pressure to the brake housing will be blocked and the springs will apply the parking brakes.
The Control Valve for the Parking Brake Is In the ON Position
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| Illustration 3 | g01067705 |
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The engine is operating. The air control valve for the parking brake is in the ON position. The secondary brake air control valve is in the OFF position. (18) Parking and secondary brake valve (30) Secondary brake air control valve (31) Air control valve for the parking brake (32) Secondary air tank (33) Parking brake reset valve (35) Secondary brake inverter valve (B) Secondary brake and parking brake switch | |
Note: The darkened lines show air pressure and the arrows show the direction of flow.
Note: Secondary brake and parking brake pressure switch (B) is activated when the air control valve for the parking brake is in the ON position.
Air pressure from secondary air tank (32) flows to the secondary brake air control valve (30) and secondary brake inverter valve (35). With secondary brake air control valve (30) in the OFF position, air pressure from the secondary air tank (32) flows through the secondary brake inverter valve (35) to parking brake air control valve (31).
When parking brake air control valve (31) is in the ON position, parking brake air control valve (31) stops the flow of air to parking and secondary brake valve (18). The parking brakes are applied by springs and the parking brakes are released by pressure. When the air flow to parking and secondary brake valve (18) is blocked, the oil pressure to the brake housing will be blocked and the springs will apply the parking brakes.
The Secondary Brake Air Control Valve Is In The ON Position.
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| Illustration 4 | g01067707 |
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The engine is operating. The air control valve for the parking brake is in the OFF position. The secondary brake air control valve is in the ON position. (18) Parking and secondary brake valve (30) Secondary brake air control valve (32) Secondary air tank (33) Parking brake reset valve (35) Secondary brake inverter valve (B) Secondary brake and parking brake pressure switch | |
Note: The darkened lines show air pressure and the arrows show the direction of flow.
Note: Secondary brake and parking brake pressure switch (B) is activated when the secondary brake air control valve is in the ON position.
Air pressure from secondary air tank (32) flows to the secondary brake air control valve (30) and secondary brake inverter valve (35). When the pedal for secondary brake air control valve (30) is partially depressed to the ON position, a portion of the full supply pressure is sent to the control passage of the secondary brake valve (35). The secondary brake inverter valve will block some of the air pressure that is flowing to the parking and secondary brake valve (18). The result is modulated secondary braking action.
When the pedal on secondary brake air control valve (30) is held in the full ON position, air pressure from secondary air tank (32) flows through the secondary brake air control valve to the control passage of the secondary brake inverter valve (35). The secondary brake inverter valve blocks all of the air pressure that was flowing to the parking and secondary brake valve (18). The parking brakes are applied by springs and the parking brakes are released by pressure. When the air flow to parking and secondary brake valve (18) is blocked, the oil pressure to the brake housing will be blocked and the springs will apply the parking brakes.
When you release the pedal for the secondary brake air control valve (30), the pedal is returned by a spring to the OFF position. When the secondary brake valve is in the OFF position, air is not sent to the control passage of the secondary brake inverter valve (35). The secondary brake inverter valve (35) allows air pressure from the secondary air tank (32) to flow to parking and secondary brake valve (18). This air flow will cause parking and secondary brake control valve (18) to send oil to the brake housing. The oil pressure will release the parking brakes.
The Service Brake Air Control Valve Is In The ON Position
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| Illustration 5 | g01067710 |
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The engine is operating. The air control valve for the parking brake is in the OFF position. The secondary brake air control valve is in the OFF position. The service brake air control valve is in the ON position. (4) Primary air tank (12) Brake air relay valve (13) Brake air relay valve for the Automatic Retarder Control (ARC) (17) Double check valve (19) Torque converter and front brake cooling diverter valve (20) Front brake master cylinder (21) Rear brake master cylinders (25) Service brake air control valve (33) Parking brake reset valve (43) Brake air relay valve for the pulled unit (44) Master cylinders for the pulled unit (B) Secondary brake and parking brake pressure switch (D) Service brake and retarder pressure switch (E) Stop lights pressure switch | |
Note: The darkened lines show air pressure and the arrows show the direction of air flow.
Note: Air pressure switches (D) and (E) are activated when the service brakes are applied or when the retarder is used.
Note: The secondary brake and the parking brake pressure switch (B) are deactivated when the air control valve for the parking brake and the air control valve for the secondary brake are in the OFF position. The parking brakes are released.
When the pedal on service brake air control valve (25) is pushed down, air pressure from primary air tank (4) flows through service brake air control valve (25) and through double check valve (17). Some of this air pressure flows through double check valve (17) to torque converter and front brake cooling diverter valve (19). Air pressure at torque converter and front brake cooling diverter valve (19) causes oil to flow through the torque converter and front brake cooling oil cooler. The rest of the air pressure flows to another check valve (17). Some of this air pressure flows to the control passage of brake air relay valve (12). This allows supply air from primary air tank (4) to flow through brake air relay valve (12) to front brake master cylinder (20) and to rear brake master cylinder (21). The double check valve above the brake master cylinders closes the passages to brake air relay valve (13) for the Automatic Retarder Control (ARC). The rest of the air pressure flows to the control passage of brake air relay valve (43) for the pulled unit. Air pressure at the control passage of brake air relay valve (43) allows supply air from primary air tank (4) to flow through brake air relay valve (43). From brake air relay valve (43), air flows to master cylinder (44) for the pulled unit. Oil pressure from the brake master cylinders flows to the wheel brakes. The oil pressure activates the brakes.
When the pressure on the pedal of service brake air control valve (25) is released, the flow of air through service brake air control valve (25) is blocked. Air pressure between the control passages of brake air relay valves (12) and (43) and service brake air control valve (25) flows outward through an exhaust passage in service brake air control valve (25). The air pressure between brake air relay valve (12) and the brake master cylinders flows outward through an exhaust passage in the brake air relay valve (12). The air pressure between brake air relay valve (43) and the brake master cylinders flows outward through an exhaust passage in the brake air relay valve (43). The oil pressure that had applied the brakes returns to the brake master cylinders as the pistons are drawn up by the spring in the brake master cylinders.
When the air pressure to the control passage of diverter valve (19) is blocked, the oil bypasses the torque converter and front brake cooling oil cooler.
The Retarder Air Control Valve Is In The ON Position
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| Illustration 6 | g01067890 |
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The engine is operating. The air control valve for the parking brake is in the OFF position. The air control valve for the secondary brake is in the OFF position. The retarder air control valve is in the ON position. (4) Primary air tank (12) Brake air relay valve (13) Brake air relay valve for the Automatic Retarder Control (ARC) (17) Double check valve (19) Torque converter and front brake cooling diverter valve (20) Front brake master cylinder (21) Rear brake master cylinders (29) Retarder air control valve (33) Parking brake reset valve (43) Brake air relay valve for the pulled unit (44) Master cylinders for the pulled unit (B) Secondary brake and parking brake pressure switch (D) Service brake and retarder pressure switch (E) Stop lights pressure switch (G) Manual retarder pressure switch | |
Note: The darkened lines show air pressure and the arrows show the direction of flow.
Note: Air pressure switches (D), (E), and (G) are activated when the retarder is applied.
Note: The secondary brake and parking brake pressure switch (B) is deactivated when the air control valve for the parking brake and the air control valve for the secondary brake are in the OFF position. The parking brakes are released.
When the lever for retarder air control valve (29) is in the ON position, air pressure from primary air tank (4) flows through retarder air control valve (29) and through four double check valves (17). Some of this air flows through double check valve (17) to torque converter and front brake cooling diverter valve (19). Air pressure at torque converter and front brake cooling diverter valve (19) causes oil to flow through the torque converter and front brake cooling oil cooler. Some of the air pressure flows through double check valves (17) to the control passage of brake air relay valve (12). This allows supply air from primary air tank (4) to flow through brake air relay valve (13) to front brake master cylinder (20) and to rear brake master cylinder (21). The double check valve that is above the brake master cylinders closes the passages to brake air relay valve (13) for the Automatic Retarder Control (ARC). The rest of the air pressure flows to the control passage of brake air relay valve (43) for the pulled unit. Air pressure at the control passage of brake air relay valve (43) allows supply air from primary air tank (4) to flow through brake air relay valve (43). From brake air relay valve (43), the air flows to master cylinder (44) for the pulled unit. Oil pressure from the brake master cylinders flows to the wheel brakes. The oil pressure activates the brakes. The engine speed must be kept between 1500 rpm and 1900 rpm in order to keep the oil to the brakes cool.
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Do not increase speed while the retarder is ON. |
The pressure of the air to the brake master cylinders is determined by the position of the lever for the retarder air control valve. When the lever is completely pulled down, the maximum amount of retarding is achieved.
When retarder air control valve (29) is in the OFF position, the flow of air through retarder air control valve (29) is blocked. Air pressure between the control passages of brake air relay valve (12) and (43) and retarder air control valve (29) flows outward through an exhaust passage in retarder air control valve (29). The air pressure between brake air relay valve (12) and the brake master cylinders flows outward through an exhaust passage in the brake air relay valve (12). The air pressure between brake air relay valve (43) and the brake master cylinders flows outward through an exhaust passage in the brake air relay valve (43). The oil pressure that had applied the brakes returns to the brake master cylinders as the pistons are drawn up by the spring in the brake master cylinders.
When the air pressure to the control passage of diverter valve (19) is blocked, the oil bypasses the torque converter and front brake cooling oil cooler.
Automatic Retarder Control (ARC) Is In The ON Position
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| Illustration 7 | g01067955 |
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The engine is operating. The air control valve for the parking brake is in the OFF position. The air control valve for the secondary brake is in the OFF position. The Automatic Retarder Control is ON. (4) Primary air tank (12) Brake air relay valve (13) Brake air relay valve for the Automatic Retarder Control (ARC) (17) Double check valve (19) Torque converter and front brake cooling diverter valve (20) Front brake master cylinder (21) Rear brake master cylinders (33) Parking brake reset valve (34) Automatic Retarder Control valve (43) Brake air relay valve for the pulled unit (44) Master cylinders for the pulled unit (B) Secondary brake and parking brake pressure switch (D) Service brake and retarder pressure switch (E) Stop lights pressure switch (F) Automatic Retarder Control pressure switch (G) Manual retarder pressure switch | |
Note: The darkened lines show air pressure and the arrows show the direction of flow.
Note: Air pressure switches (D) and (E) are activated when the service brake is applied.
Note: Air pressure switches (D), (E), and (G) are activated when the manual retarder is applied.
Note: Air pressure switches (F) and (G) are activated when the Automatic Retarder Control (ARC) is in the ON position.
Note: The secondary brake and parking brake pressure switch (B) is deactivated when the air control valve for the parking brake and the air control valve for the secondary brake are in the OFF position. The parking brakes are released.
When Automatic Retarder Control (ARC) is ON, the retarder will be used to keep the engine speed constant. Air pressure from primary air tank (4) flows through Automatic Retarder Control valve (34). Some of this air flows through two double check valves (17). This air pressure flows to torque converter and front brake cooling diverter valve (19). Air pressure at torque converter and front brake cooling diverter valve (19) causes oil to flow through the torque converter and front brake cooling oil cooler. Some of the air pressure flows to the control passage of brake air relay valve (13). This allows supply air from primary air tank (4) to flow through brake air relay valve (13) to front brake master cylinder (20) and to rear brake master cylinders (21). The double check valve above the brake master cylinders closes the passages to brake air relay valve (12) for the service brakes and for the manual retarder. The rest of the air pressure flows to the control passage of brake air relay valve (43) for the pulled unit. Air pressure at the control passage of brake air relay valve (43) allows supply air from primary air tank (4) to flow through brake air relay valve (43). From brake air relay valve (43) for the pulled unit, air flows to master cylinder (44) for the pulled unit. Oil pressure from the brake master cylinders flows to the wheel brakes. The oil pressure activates the brakes.
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Do not increase speed while the retarder is ON. |
The pressure of the air to the brake master cylinders is determined by a proportional solenoid on Automatic Retarder Control valve (34).
When retarding is not needed, the flow of air through Automatic Retarder Control valve (34) is blocked. Air pressure between the control passages of brake air relay valve (13) and (43) and Automatic Retarder Control valve (34) flows outward through an exhaust passage in Automatic Retarder Control valve (34). The air pressure between brake air relay valve (13) and the brake master cylinders flows outward through an exhaust passage in the brake air relay valve (13). The air pressure between brake air relay valve (43) and the brake master cylinders flows outward through an exhaust passage in the brake air relay valve (43). The oil pressure that had applied the brakes returns to the brake master cylinders as the pistons are drawn up by the spring in the brake master cylinders.
When the air pressure to the control passage of diverter valve (19) is blocked, the oil bypasses the torque converter and front brake cooling oil cooler.
The Air Control Valve (Pulled Unit) Is In The ON Position
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| Illustration 8 | g01068096 |
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| Illustration 9 | g01068047 |
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The engine is operating. The air control valve for the parking brake is in the OFF position. The air control valve for the secondary brake is in the OFF position. The air control valve for the pulled unit is in the ON position. (4) Primary air tank (17) Double check valve (33) Parking brake reset valve (40) Air control valve for the pulled unit (43) Brake air relay valve (44) Master cylinders for the pulled unit | |
Note: The darkened lines show air pressure and the arrows show the direction of flow.
Note: Air pressure switch (E) is activated when the pulled unit brake is applied.
When the lever for air control valve (40) for the pulled unit is in the ON position, air pressure from primary air tank (4) flows through air control valve (40) for the pulled unit and through double check valve (17). The air pressure flows to the control passage of the brake air relay valve (43). Air pressure at the control passage of brake air relay valve (43) allows supply air from primary air tank (4) to flow through brake air relay valve (43) to master cylinders (44). Oil pressure from the brake master cylinders flows to the wheel brakes on the pulled unit. The oil pressure activates the brakes.
The pressure of the air to the brake master cylinders is determined by the position of the lever for the air control valve for the pulled unit. When the lever is completely pulled down, the maximum amount of braking is achieved.
When air control valve (40) for the pulled unit is in the OFF position, the flow of air through air control valve (40) for the pulled unit is blocked. Air pressure between the control passages of brake air relay valve (43) and air control valve (40) for the pulled unit flows outward through an exhaust passage in air control valve (40) for the pulled unit. The air pressure between brake air relay valve (43) and the brake master cylinders flows outward through an exhaust passage in the brake air relay valve (43). The oil pressure that had applied the brakes returns to the brake master cylinders as the pistons are drawn up by the spring in the brake master cylinders.