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Pressurized system: Hot coolant can cause serious burn. To open cap, stop engine, wait until radiator is cool. Then loosen cap slowly to relieve the pressure. |
To relieve the pressure from the coolant system, move the engine start switch to the OFF position. Allow the cooling system pressure cap to cool. The cap must be cool enough to touch with a bare hand. Remove the cooling system pressure cap slowly in order to relieve pressure.
To relieve the pressure from the fuel system, turn off the engine.
High Pressure Fuel Lines (If Equipped)
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Contact with high pressure fuel may cause fluid penetration and burn hazards. High pressure fuel spray may cause a fire hazard. Failure to follow these inspection, maintenance and service instructions may cause personal injury or death. |
The high-pressure fuel lines are the fuel lines that are between the high-pressure fuel pump and the high-pressure fuel manifold and the fuel lines that are between the fuel manifold and cylinder head.
These fuel lines are different from fuel lines on other fuel systems for the following reasons:
- The high-pressure fuel lines are constantly charged with high pressure.
- The internal pressures of the high-pressure fuel lines are higher than other types of fuel system.
Before any service or repair is performed on the engine fuel lines, perform the following tasks:
- Stop the engine.
- Wait for 10 minutes.
Note: Fuel pressure can be monitored by Caterpillar Electronic Technician (ET).
Do not loosen the high-pressure fuel lines in order to purge trapped air from the fuel system.
To relieve the pressure from the engine oil system, turn off the engine.
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Personal injury can result from hydraulic oil pressure and hot oil. Hydraulic oil pressure can remain in the hydraulic system after the engine has been stopped. Serious injury can be caused if this pressure is not released before any service is done on the hydraulic system. Make sure all of the attachments have been lowered, oil is cool before removing any components or lines. Remove the oil filler cap only when the engine is stopped, and the filler cap is cool enough to touch with your bare hand. |
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Personal injury or death can result from sudden machine movement. Sudden movement of the machine can cause injury to persons on or near the machine. To prevent injury or death, make sure that the area around the machine is clear of personnel and obstructions before operating the machine. |
- Park on a level surface and lower the work tools to the ground.
- Engage the parking brake.
- Shut off the engine.
This machine has two separate hydraulic systems and two separate hydraulic oil tanks. Both hydraulic oil tanks are equipped with a breaker relief valve that is used to relieve pressure in each one of the hydraulic oil tanks.
Reference: Refer to this Operation and Maintenance Manual, "Hydraulic System Oil (Implement) (Hydraulic Fan) - Change" for information about the location and operation of the breaker relief valve for the implement and hydraulic fan hydraulic system.
Refer to this Operation and Maintenance Manual, "Hydraulic System Oil (Steering, Brake) - Change" for information about the location and operation of the breaker relief valve for the steering and brake hydraulic system.
Slowly loosen the hydraulic oil tank filler cap of each hydraulic oil tank. This action will confirm that there is no build-up of pressure in either one of the hydraulic oil tanks.
Use the following procedures in order to release the hydraulic pressure from the implement system.
- Make sure that the area around the machine is clear of personnel and obstructions before performing this procedure.
- Turn the key to the ON position before moving the control levers.
- Move the implement control levers through the full range of travel for each control lever. This procedure will relieve any pressure that may be present in the implement hydraulic system.
- Move the engine start switch to the OFF position.
Note: Additional procedures that provide for the manual release of implement system pressure are described in following sections of this article. Refer to "Lift Cylinder Circuit" and "Tilt Cylinder Circuit" in order to release the hydraulic system pressure from the appropriate circuit.
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Personal injury or death may occur from failure to adhere to the following warnings. Keep all personnel away from the boom drop area when lowering the boom with the engine stopped. Keep all personnel away from the front linkage when lowering the boom. |
Use the following procedure to release the lift cylinder hydraulic pressure manually.
- Make sure that the area around the machine is clear of personnel and obstructions before performing this procedure.
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Illustration 1 g03611076 Machine location and detail view of ball valve used to manually lower work tool. - A ball valve is used for manually lowering the work tool. This ball valve is located in the articulation joint on the left-hand side of the front frame of the machine. The ball valve is mounted on a bracket that is at nearly the same level as the drive shaft. Slowly turn the square stem in the clockwise direction. The square stem should be rotated 90 degrees.
- Rotate the square stem counterclockwise 90 degrees once the pressure has been released from the lift cylinder circuit.
Refer to this Operation and Maintenance Manual, "Equipment Lowering with Engine Stopped" for additional information.
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Hot oil and hot components can cause personal injury. Do not allow hot oil or hot components to contact skin. |
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Care must be taken to ensure that fluids are contained during performance of inspection, maintenance, testing, adjusting, and repair of the product. Be prepared to collect the fluid with suitable containers before opening any compartment or disassembling any component containing fluids. Refer to Special Publication, NENG2500, "Dealer Service Tool Catalog" for tools and supplies suitable to collect and contain fluids on Cat® products. Dispose of all fluids according to local regulations and mandates. |
Use the following procedure to release the tilt cylinder hydraulic pressure manually.
- Make sure that the area around the machine is clear of personnel and obstructions before performing this procedure.
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Illustration 2 g03611096 Two bleeder screws located on the tilt circuit hydraulic control valve. - Locate the tilt circuit hydraulic control valve on the left-hand side of the machine. This control valve is mounted on the inside of the front frame near the articulation joint.
- Connect a suitable hose to each bleeder screw that is located on top of the hydraulic control valve.
- Oil will escape from the hydraulic system when the bleeder screws are loosened. Direct the open end of each hose into a suitable container.
Note: Refer to Operation and Maintenance Manual, "General Hazard Information" for information on containing fluid spillage.
- Slowly open the bleeder screws to a maximum of 1/2 turn to allow the oil pressure to be released from the hydraulic system. Be certain that the bleeder screw hoses remain directed into the appropriate container.
- Close the bleeder screws and remove the hoses when the pressure is released from the tilt circuit. Do not allow the oil that is contained in the hose to spill.
- The oil that is collected during this procedure must be disposed of according to local regulations.
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Hot oil and hot components can cause personal injury. Do not allow hot oil or hot components to contact skin. |
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Care must be taken to ensure that fluids are contained during performance of inspection, maintenance, testing, adjusting, and repair of the product. Be prepared to collect the fluid with suitable containers before opening any compartment or disassembling any component containing fluids. Refer to Special Publication, NENG2500, "Dealer Service Tool Catalog" for tools and supplies suitable to collect and contain fluids on Cat® products. Dispose of all fluids according to local regulations and mandates. |
Note: Hydraulic steering system pressure will be automatically released from the system after the engine has been shut off for several minutes. Use the following procedure to confirm that system pressure has been released automatically. You may also use this procedure to cause system pressure release to occur in less time.
Use the following procedure to release the hydraulic steering system pressure manually.
- Make sure that the area around the machine is clear of personnel and obstructions before performing this procedure.
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Illustration 3 g03611116 Steering system bleeder screws - Two bleeder screws are located on the hydraulic steering system control valve. This valve is mounted on the inside of the right-hand frame rail in front of the rear axle. Lower the bottom guard below the control valve, if necessary, to allow greater access to the bleeder screws.
- Connect a suitable hose to each bleeder screw that is located on the bottom of the steering system control valve.
- Oil will escape from the steering system circuit when the bleeder screws are loosened. Direct the open end of each hose into a suitable container.
Note: Refer to Operation and Maintenance Manual, "General Hazard Information" for information on containing fluid spillage.
- Slowly open the bleeder screws to a maximum of 1/2 turn to allow the oil pressure to be released from the steering system. Be certain that the bleeder screw hoses remain directed into the appropriate container.
- Close the bleeder screws and remove the hoses when the pressure is released from the steering system. Do not allow the oil that is contained in the hose to spill.
- The oil that is collected during this procedure must be disposed of according to local regulations.
- Raise, and securely fasten, the bottom guard if the guard was lowered in step 2.
The key may be in either the ON position or the OFF position before pressing the brake pedal.
Depress the brake pedal repeatedly in order to relieve any pressure that may be present in the brake hydraulic system.
If turned to the ON position, move the key to the OFF position.
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Hydraulic accumulator contains gas and oil under high pressure. Improper removal or repair procedures could cause severe injury. To remove or repair, instructions in the service manual must be followed. Special equipment is required for testing and charging. |
Relieving the pressure in the brake circuit will not release the nitrogen precharge pressure in the brake accumulators.