Schematic
| Hoist and brake cooling schematic with shallow brake cooling arrangement (10) Front Brake Oil Cooler (11) Rear Brake Oil Coolers (12) Hydraulic Tank (Brake, Hoist, Steering) (19) Rear Brakes (20) Passage from Control Valve (Brake Cooling, Hoist) (21) Front Brakes (22) Rear Temperature Sensors (Brake Oil) (23) Passage to the brake oil filter (24) Brake Cooling Screen (25) Front Temperature Sensors (Brake Oil) (26) Gear Pump (Brake Cooling) (27) Passage to the lube system for the rear axle (28) Oil Filter (Brake Cooling, Hoist)(29) Check Valves (Hydraulic Tank) |
Location of Components
| 797F components for the shallow brake cooling system (1) Gear Pump (Brake Cooling, Hoist) (7) Control Valve (Brake Cooling, Hoist) (10) Front Brake Oil Cooler (11) Rear Brake Oil Coolers (12) Hydraulic Tank (Brake, Hoist, Steering) (14) Pump Drive (24) Brake Cooling Screen(26) Gear Pump (Brake Cooling) |
| 797F components for the shallow brake cooling system (9) Hoist Cylinders (10) Front Brake Oil Cooler (11) Rear Brake Oil Coolers (12) Hydraulic Tank (Brake, Hoist, Steering)(28) Oil Filter (Brake Cooling, Hoist) |
Operation
The 797F truck is equipped with either the Shallow Brake Cooling Arrangement or the Steep Brake Cooling Arrangement which is for downhill applications. The Steep Brake Cooling Arrangement is similar to the brake cooling system for the 797B truck. The Shallow Brake Cooling Arrangement is new on the 797F truck.
Note: The 797F XQ Off-Highway Truck uses the steep brake cooling system and not the shallow brake cooling system.
The brake cooling system supplies oil in order to cool the parking and service brakes. The brake cooling oil shares the same section of Hydraulic Tank (Brake, Hoist, Steering) (12) as the hoist oil.
| Right inside frame rail (1) Gear Pump (Brake Cooling, Hoist) (7) Control Valve (Brake Cooling, Hoist) (14) Pump Drive (24) Brake Cooling Screen(26) Gear Pump (Brake Cooling) |
Gear Pump (Brake Cooling) (26) is attached to the bottom rear of Pump Drive (14) directly below Gear Pump (Brake Cooling, Hoist) (1). Gear Pump (Brake Cooling) (26) sends oil through Brake Cooling Screen (24), Front Brake Oil Cooler (10), Rear Brake Oil Cooler (11), and one Oil Filter (Brake Cooling, Hoist) (28) to Front Brakes (21) and to Rear Brakes (19). Oil from Control Valve (Brake Cooling, Hoist) (7) also flows through Front Brake Oil Cooler (10), Rear Brake Oil Cooler (11), and one Oil Filter (Brake Cooling, Hoist) (28) in order to provide additional cooling oil to Front Brakes (21) and to Rear Brakes (19) .
Front Temperature Sensors (Brake Oil) (25) and Rear Temperature Sensors (Brake Oil) (22) send a signal to the Brake ECM which indicates the temperature of the brake oil. Check Valves (29) in the hydraulic tank maintain a minimum pressure in the brake cooling hydraulic system. Cooling oil from Front Brakes (21) and Rear Brakes (19) returns to Hydraulic Tank (Brake, Hoist, Steering) (12) through the brake cooling return port on the top of the tank.
Brake Cooling System (Steep Grade)
Schematic
| Hoist and brake cooling schematic with steep brake cooling arrangement (10) Front Brake Oil Cooler (11) Rear Brake Oil Coolers (12) Hydraulic Tank (Brake, Hoist, Steering) (15) Piston Pump (Brake Cooling) (19) Rear Brakes (20) Passage from Control Valve (Brake Cooling, Hoist) (21) Front Brakes (22) Rear Temperature Sensors (Brake Oil) (24) Brake Cooling Screen (25) Front Temperature Sensors (Brake Oil) (28) Oil Filter (Brake Cooling, Hoist) (30) Passage from pressure reducing valve (31) Gear Pump (Brake Cooling) (Extra Retarding)(32) Piston Motor (Brake Cooling) |
Note: The 797F XQ Off-Highway Truck uses the steep brake cooling system and not the shallow brake cooling system.
Location of Components
| 797F components for the steep brake cooling system (1) Gear Pump (Brake Cooling, Hoist) (7) Control Valve (Brake Cooling, Hoist) (10) Front Brake Oil Cooler (11) Rear Brake Oil Coolers (12) Hydraulic Tank (Brake, Hoist, Steering) (14) Pump Drive (15) Piston Pump (Brake Cooling) (24) Brake Cooling Screen (31) Gear Pump (Brake Cooling) (Extra Retarding)(32) Piston Motor (Brake Cooling) |
| 797F components for the shallow brake cooling system (7) Control Valve (Brake Cooling, Hoist) (10) Front Brake Oil Cooler (11) Rear Brake Oil Coolers (12) Hydraulic Tank (Brake, Hoist, Steering) (24) Brake Cooling Screen (28) Oil Filter (Brake Cooling, Hoist)(32) Piston Motor (Brake Cooling) |
Operation
Note: The 797F XQ Off-Highway Truck uses the steep brake cooling system and not the shallow brake cooling system.
| Differences Between Components of Steep Brake Cooling and Shallow Brake Cooling Arrangements | |||
| Component | Shallow | Steep | Comments |
| Piston Motor (Brake Cooling) (32) | 0 | 1 | The piston motor for the steep brake cooling arrangement is attached to the hydraulic tank. |
| Piston Pump (Brake Cooling) (15) | 0 | 1 | |
| Gear Pump (Brake Cooling) (26) | 1 | 0 | The gear pump for the shallow brake cooling arrangement is located directly beneath the Gear Pump (Hoist and Brake Cooling). |
| Gear Pump (Brake Cooling) (Extra Retarding) (31) | 0 | 1 | The gear pump for the steep brake cooling arrangement is located on the inside of the hydraulic tank. |
| Brake Cooling Screens (24) | 1 | 2 | The steep brake cooling arrangement has an additional screen. Both screens are attached to the hydraulic tank. |
| Rear Brake Oil Coolers (11) | 1 | 2 | |
| Oil Filters (Brake Cooling, Hoist) (28) | 1 | 2 | The steep brake cooling arrangement has an additional oil filter on the left side of the truck to the rear of the left front suspension cylinder. |
| Right inside frame rail (1) Gear Pump (Brake Cooling, Hoist) (14) Pump Drive(15) Piston Pump (Brake Cooling) |
In the Steep Brake Cooling Arrangement, oil from Piston Pump (Brake Cooling) (15) drives Piston Motor (Brake Cooling) (32). Piston Motor (Brake Cooling) (32) drives Gear Pump (Brake Cooling) (Extra Retarding) (31) which is located inside Hydraulic Tank (Brake, Hoist, Steering) (12). Oil from one section of Gear Pump (Brake Cooling) (Extra Retarding) (31) flows through Brake Cooling Screen (24), Front Brake Oil Cooler (10), and two Oil Filters (Brake Cooling, Hoist) (28) to Front Brakes (21). Oil from Control Valve (Brake Cooling, Hoist) (7) flows through Front Brake Oil Cooler (10) and two Oil Filters (Brake Cooling, Hoist) (28) in order to provide additional cooling oil to Front Brakes (21) .
Oil from two sections of Gear Pump (Brake Cooling) (Extra Retarding) (31) flows through Brake Cooling Screen (24) and two Rear Brake Oil Coolers (11) to Rear Brakes (19). Oil from Control Valve (Brake Cooling, Hoist) (7) flows through two Rear Brake Oil Coolers (11) in order to provide additional cooling oil to Rear Brakes (19) .
The Brake/Cooling ECM controls a solenoid on Piston Pump (Brake Cooling) (15). When the brake oil temperature is less than 102 °C (215 °F), the brake cooling drive pump is turned OFF and no oil will flow from the brake cooling pumps. When the brake oil temperature is greater than 102 °C (215 °F), the Brake/Cooling ECM sends a PWM signal to Piston Pump (Brake Cooling) (15) in order to modulate the brake cooling flow from the pumps. When the brake oil temperature is greater than 107 °C (225 °F), the Brake/Cooling ECM sends a signal to the brake cooling drive pump in order to provide maximum brake cooling flow from the pumps.
MARYGAR
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