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| Illustration 1 | g01066251 |
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The control valve for the hoist and for brake cooling is shown in the RAISE position. (1) Left rear wheel brake (2) Rear brake oil coolers (3) Rear brake oil cooler screen (4) Diverter valve for rear brake cooling (5) Control valve for hoist and brake cooling (6) Front brake oil coolers (7) Front brake oil cooler screen (8) Left front wheel brake (9) Hoist screens (10) Oil filter for the left front brake cooling oil (11) Gear pumps for the hoist and for the brake cooling (12) Hydraulic fan drive system (13) Steering system (14) Gear pump for brake actuation (15) Pump drive (16) Hoist manifold (17) Oil filter for the right front brake cooling oil (18) Gear pump for the motor drive for the rear axle oil pump (19) Oil filter for the steering and fan drive systems (20) Brake cooling drive pump (21) Piston pump for the hydraulic fan drive system (22) Chassis/brake valve (23) Oil cooler for the steering and fan drive systems (24) Screens for the front and rear cooling pumps (25) Piston pump for the steering system (26) Right front wheel brake (27) Hydraulic tank (28) Right rear wheel brake (29) Steering hydraulic tank (30) Oil cooler relief valves (31) Brake cooling pump for front brake cooling (32) Brake cooling pumps for rear brake cooling (33) Drive motor for brake cooling (34) Hoist cylinders (35) Hoist control valve | |
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| Illustration 2 | g01066450 |
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Rear view JSM1-146 (5) Control valve for hoist and brake cooling (9) Hoist screens (11) Gear pumps for the hoist and for the brake cooling (16) Hoist manifold (27) Hydraulic tank (34) Hoist cylinders (35) Hoist control valve | |
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| Illustration 3 | g01066453 |
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Rear view JSM147-Up (5) Control valve for hoist and brake cooling (9) Hoist screens (11) Gear pumps for the hoist and for the brake cooling (16) Hoist manifold (27) Hydraulic tank (34) Hoist cylinders (35) Hoist control valve | |
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| Illustration 4 | g01066458 |
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Top view JSM1-146 (5) Control valve for hoist and brake cooling (9) Hoist screens (27) Hydraulic tank (33) Drive motor for Brake cooling (34) Hoist cylinders | |
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| Illustration 5 | g01066459 |
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Top view JSM147-Up (5) Control valve for hoist and brake cooling (9) Hoist screens (27) Hydraulic tank (33) Drive motor for Brake cooling (34) Hoist cylinders | |
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| Illustration 6 | g01066460 |
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View A-A JSM1-146 (9) Hoist screens (11) Gear pumps for the hoist and for the brake cooling (15) Pump drive (20) Piston pump for the motor drive for the gear pumps for brake cooling (21) Piston pump for the hydraulic fan drive system (27) Hydraulic tank (34) Hoist cylinders | |
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| Illustration 7 | g01066462 |
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View A-A JSM147-Up (9) Hoist screens (11) Gear pumps for the hoist and for the brake cooling (15) Pump drive (20) Piston pump for the motor drive for the gear pumps for brake cooling (21) Piston pump for the hydraulic fan drive system (27) Hydraulic tank (34) Hoist cylinders | |
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| Illustration 8 | g01066554 |
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Hoist lever (A) RAISE position (B) HOLD position (C) FLOAT position (D) LOWER position | |
The hoist system is electronically controlled by the Chassis ECM. The hoist system is similar in operation to other Caterpillar off-highway trucks. The system consists of the following four operating positions:
- RAISE position (A)
- HOLD position (B)
- FLOAT position (C)
- LOWER position (D)
The truck should normally be operated with the hoist lever in the FLOAT position. Operating the truck with the hoist in the FLOAT position will ensure that the weight of the truck body is located on the frame and body pads.
Note: The weight of the truck body will be supported by the hoist cylinders if the truck is not operated with the hoist lever in the FLOAT position.
The Chassis ECM and the hoist control valve also provide the following functions for the hoist control that are not controlled by the operator:
- LOWER SNUB control
- OVERCENTER control
- RAISE SNUB control
LOWER SNUB control occurs while the truck body is being lowered to the DOWN position. Before the truck body contacts the truck frame, the Chassis ECM signals the hoist solenoids to move the hoist valve spools to the LOWER SNUB position. This will occur when the truck body is approximately located between 4 degrees to 15 degrees in relation to the truck frame. In the LOWER SNUB position, the float speed of the truck body is reduced in order to prevent the truck body from contacting the truck frame too hard.
OVERCENTER control prevents cavitation of the hoist cylinders by preventing the truck body from raising faster that is allowed by the system. This condition may occur if there is a sudden shift in the location of the load. While the truck body is being raised, the Chassis ECM signals the hoist solenoids to move the hoist valve spools to the OVERCENTER position when the truck body is approximately at a 40 degree angle.
RAISE SNUB control occurs when the truck body is being raised and the hoist cylinders are almost extended. The truck body will be approximately at a 55 degree angle. The Chassis ECM signals the hoist solenoids to move the hoist valve spools to the RAISE SNUB position. In the RAISE SNUB position, the raise speed of the truck body is reduced in order to prevent the hoist cylinder pistons from making hard contact with the cylinder heads.
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| Illustration 9 | g01066464 |
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Right inside frame rail JSM1-146 (9) Front and rear hoist screens (36) Hoist screen bypass switch | |
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| Illustration 10 | g01066465 |
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Right inside frame rail JSM147-Up (9) Front and rear hoist screens (36) Hoist screen bypass switches | |
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| Illustration 11 | g01066466 |
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Right inside frame rail (11) Gear pumps for the hoist and for the brake cooling (37) Pressure taps | |
The gear pump for the hoist and brake cooling (11) pulls oil from hydraulic tank (27). Oil flows from the two front pump sections and combines at front hoist screen (9). Oil then flows from the front hoist screen to the control valve for the hoist and brake cooling (5). From the hoist and brake cooling valve, oil may flow in one of two directions. The oil may flow to hoist cylinders (34), or the oil may flow to diverter valve (4), to rear brake oil coolers (2), to left rear brake (1), and to right rear brake (28).
Oil flows from the two rear pump sections and combines at rear hoist screen (9). Oil flows from the rear hoist screen to the control valve for the hoist and brake cooling (5). Oil then flows to hoist cylinders (34) or to front brake oil coolers (6), left front brake cooling oil filter (10), right front brake cooling oil filter (17), left front brake (8), and right front brake (26).
There is a bypass valve that is located inside the housing of each hoist screen. The bypass valves will open in order to protect the hoist system if the screens become restricted. Hoist screen bypass switch (36) is also located on the housing of each hoist screen. The bypass switches provide input signals to the Chassis ECM. The Chassis ECM sends the signals to the Vital Information Management System (VIMS). VIMS will then inform the operator if the hoist screens are restricted.
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| Illustration 12 | g01066468 |
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Left inside frame rail (2) Rear brake oil coolers (4) Diverter valve for rear brake cooling (38) Solenoid valve for brake oil diverter (39) Pilot signal line for the diverter valve | |
Rear brake cooling oil flows through diverter valve (4). The diverter valve is located behind rear brake oil coolers (2) on the inside of the left frame rail. When the oil temperature is greater than
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| Illustration 13 | g01066469 |
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Right inside frame rail (11) Gear pumps for the hoist and for the brake cooling (15) Pump drive (20) Brake cooling drive pump | |
Brake cooling drive pump (20) is attached to the bottom rear of pump drive (15) directly below the gear pumps for the hoist and brake cooling (11). Oil flows from the brake cooling drive pump (20) to the drive motor for brake cooling (33). The drive motor for brake cooling (33) drives both brake cooling pumps for rear brake cooling (32) and one brake cooling pump for front brake cooling (31). The brake cooling pumps are located within hydraulic tank (27). Oil that is pumped from brake cooling pump (31) is joined with the oil for the hoist in order to cool the front brakes. Oil that is pumped from brake cooling pump (32) is joined with the oil for the hoist in order to cool the rear brakes.
The Brake/Cooling ECM controls a solenoid on brake cooling drive pump (20). When the brake oil temperature is less than
Note: Refer to Systems Operation and Testing and Adjusting, "Braking System" for more information on the braking system.
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| Illustration 14 | g01066477 |
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Brake cooling filter for the right front brake (40) Pressure tap for unfiltered brake cooling oil pressure (41) Hose (42) Pressure tap for filtered brake cooling oil pressure (43) Bypass valve (44) Scheduled Oil Sampling (S·O·S) port (45) Bypass switch | |
There are two front brake cooling oil filters for the front brakes. One brake cooling oil filter (10) is for the left front brake. The filter is located on the outside of the left side frame rail. The right front brake oil cooler filter (17) is located on the outside of the right side frame rail. Pressure taps are located on the top of each the brake cooling oil filters. Pressure tap (40) is used to measure unfiltered oil pressure. Pressure tap (42) is used to measure filtered oil pressure. Together, the two taps are used to calculate the filter restriction within the front brake cooling oil filter.
Oil samples for front brake cooling are taken from Scheduled Oil Sampling (S·O·S) port (44). The sampling port is located on top of the filter housing.
Bypass valve (43) is located within the filter housing of the cooling filter. Bypass valve (43) will open in order to protect the front brake cooling oil system if the filter becomes restricted. Bypass switch (45) is also located on the filter housing. Bypass switch (45) provides input signals to the Brake/Cooling ECM. The Brake/Cooling ECM sends the signals to VIMS. VIMS warns the operator if the front brake oil cooler filter is restricted.
Filtered brake cooling oil flows from the front brake oil cooler filter through hose (41) to the hydraulic tank for brake actuation. The oil flow is used to ensure that the hydraulic tank for brake actuation remains full of oil.
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| Illustration 15 | g01066471 |
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Left inside frame rail (22) Chassis/brake valve (38) Solenoid valve brake oil diverter (46) Pressure reducing valve pilot oil for the hoist | |
Chassis/brake valve (22) is located on the left inner frame rail in front of the brake accumulators. The pilot oil for the hoist is controlled at chassis/brake valve (22) by pressure reducing valve (46). The pilot oil flows to hoist manifold (16). The "ON/OFF" solenoid for the pilot oil controls the flow of pilot oil to the top and bottom of all of the directional spools in hoist control valve (35).
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| Illustration 16 | g01066472 |
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Front view of the control valve group for hoist and brake cooling (5) Control valve for hoist and brake cooling (16) Hoist manifold (35) Hoist control valve (47) Pilot solenoid valves for the hoist (48) Hose (49) Solenoids for the hoist control | |
The control valve group for the hoist and brake cooling consists of the following three sections: control valve for hoist and brake cooling (5), hoist manifold (16) and hoist control valve (35). Oil flows from gear pumps (11) to the control valve for the hoist and brake cooling (5). When the hoist cylinders are not being raised or lowered, oil flows to the brakes through the two hoses on top of the valve. Pilot oil for the hoist is drained from hoist manifold (16) through hose (48).
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| Illustration 17 | g01066474 |
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Rear view of the control valve group for hoist and brake cooling (5) Control valve for hoist and brake cooling (50) Pilot signal line (51) Pilot "ON/OFF" solenoid for the hoist | |
When the hoist cylinders are being raised or lowered, the Chassis ECM energizes pilot "ON/OFF" solenoid (51) for the hoist, two pilot solenoid valves (47) for the hoist, and two control solenoids (49) for the hoist. One control solenoid for the hoist is energized in order to provide supply oil to the head end of the hoist cylinders and another solenoid is energized in order to drain oil from the rod end of the hoist cylinders.
Pilot oil from chassis/brake valve (22) flows through pilot signal line (50) to hoist manifold (16). When the engine is started, the Chassis ECM energizes pilot "ON/OFF" solenoid (51) for the hoist. If the hoist lever remains in the HOLD position for an extended length of time, the Chassis ECM will de-energize the solenoid. Pilot "ON/OFF" solenoid (51) for the hoist is immediately re-energized if the hoist lever is moved from the HOLD position.
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| Illustration 18 | g01066476 |
The truck body is raised and lowered by twin two-stage cylinders. To lower the truck body with an inoperable engine, hoist pilot pressure is required. An electric drive pump is located behind hydraulic tank (27) on the right side of the machine. Use the electric drive pump in order to provide the pilot oil for the hoist. Use the following procedure to lower the truck body:
- Turn the engine start switch to the ON position. The electric drive pump and the hoist cylinders will be energized.
- Move the hoist lever to the RAISE position for 15 seconds. Then move the hoist lever to the FLOAT position.
- Depress the brake release switch that is located on the dashboard of the operator's cab.
Note: For more information on lowering the truck body with a inoperable engine, refer to the following information: Operation and Maintenance Manual, "Lowering the Body with the Engine Stopped", Braking System Systems Operation, "Towing" and Braking System Testing and Adjusting, "Towing the Machine - Preparation".
To raise the truck body with a inoperable engine, connect an Auxiliary Power Unit (APU) to the hoist cylinders. Use the oil ports that are located on the bottom of the left hoist cylinder. Repeat Step 1 through Step 3 in order to raise the truck body.
Note: During Step 2, do not move the hoist lever to the FLOAT position after 15 seconds. Keep the hoist lever in the RAISE position.