834G Wheel Dozer and 836G Landfill Compactor Electrohydraulic System Caterpillar

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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 escaping fluid under pressure. Escaping fluid under pressure, even a very small pin-hole size leak, can penetrate body tissue and cause serious injury and possible death. If fluid is injected into your skin, it must be treated immediately by a doctor familiar with this type of injury. Always use a board or cardboard when checking for a leak.

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Sudden movement or accidental starting of the machine can cause personal injury or death to persons on or near the machine. To prevent personal injury or death, perform the following: Park the machine on a smooth, level surface. Lower the bucket and/or attachments to the ground and engage the parking brake. Stop the engine and remove the key. Block the wheels and install the steering frame lock.

Note: This machine is equipped with an electronic control module (ECM). The implement ECM contains the system diagnostics in order to detect faults in the implement electronic control system. The diagnostics are displayed on the Caterpillar Monitoring System when the system is in the Service Mode. Make sure that all faults are corrected before you troubleshoot the following problems.

Reference: For additional information on the Implement Electronic Control System, refer to System Operation, "Implement Electronic Control System".

Reference: For additional information on troubleshooting the Implement Electronic Control System, refer to Testing and Adjusting, "Troubleshooting Diagnostic Codes".

Some of the terms that are used for troubleshooting the machine are defined below.

• Collapse is the sudden drop of an implement cylinder during normal operation.

• Drift is the creeping of the implement cylinders while the control is in the HOLD position.

• Droop is an initial movement of the hydraulic cylinders in the opposite direction of the selected lever position. The cylinders then move in the correct direction.

Problem 1: The pump makes noise and the cylinder rods do not move evenly. There are also air bubbles in the oil.

Probable causes:

• The viscosity of the oil is incorrect.

• The relief valve opens at low oil pressure.

• There is a loose connection of the oil line on the inlet side of the pump.

• The pump has too much wear.

Problem 2: The oil temperature is too high.

Probable causes:

• The machine is being operated above the intended capacity or in ambient temperatures that are too high for the machine's design.

• The viscosity of the oil is incorrect.

• The setting of the main relief valve is too low. This will cause the relief valve to open.

• The pump has too much wear.

• There is a restriction in an oil passage.

• There is a leak in one or more circuits.

• The load on the system is too high. This causes the relief valve to open.

• The oil level is low.

• The oil is contaminated.

• The air flow through the oil cooler is too low.

• The oil flow through the oil cooler is too low.

• The hydraulic oil temperature sensor is faulty.

• There is air in the hydraulic oil.

Note: A problem with air in the hydraulic oil must be corrected before the hydraulic system will operate at normal temperatures. There are two conditions that cause air to be in the hydraulic oil:

• Return oil is flowing into the hydraulic oil tank above the level of oil that is in the tank.

• There are leaks in the line between the hydraulic pump and the hydraulic oil tank.

Problem 3: The pump output is low.

Probable causes:

• The oil level is low.

• The viscosity of the oil is incorrect.

• The pump has too much wear.

Problem 4: The oil pressure is low.

Probable causes:

• The relief valve opens at low oil pressure.

• The pump has too much wear.

• An O-ring seal in the system failed.

• The control valve and the valve spool have excessive wear.

Problem 5: The Blade moves while the control lever is in the HOLD position.

Probable causes:

• The control valve and the valve spool have excessive wear.

• A piston seal in a cylinder has excessive wear.

• There is a leak between the control valve and the cylinder that has drifted.

• A check valve is not closing because of dirt or because of a worn seat.

• The control valve is not centering correctly.

• The control lever was not in the HOLD position when the engine start key was turned to the ON position. There may be dirt or the return spring may be broken.

• The lever position sensor is faulty.

• The solenoid on the pilot control actuator is faulty.

Problem 6: The Blade droops when the lift control lever is moved from HOLD to RAISE.

Probable causes:

• The oil is too cold.

• The piston seals and/or the lift cylinders are worn.

• The load check valve is not closing because the spring is weak or broken or because there is dirt or debris in the check valve.

Problem 7: The hydraulic force is too low when the lift control lever is moved to RAISE or to LOWER.

Probable causes:

• The machine is being operated improperly.

• The pilot system pressure is too low.

• The control current to the solenoid is not correct.

• The position sensor for the lift control lever is damaged.

• The relief valve setting for the ride control valve is too low while the ride control switch is ON.

• The main control valve is contaminated or damaged.

• The makeup valve is sticking.

• The pilot control actuator is contaminated or damaged.

• The main relief valve setting is too low.

Problem 8: All implement functions are sluggish.

• The oil level is low.

• The pump is worn or damaged.

• The implement electronic control module is not calibrated.

• The main relief valve setting is too low.

• The pilot relief valve is faulty.

• The hydraulic system is contaminated.

Probable causes:

Problem 9: The implement functions are erratic or intermittent.

Probable causes:

• The oil level is low.

• The pump has too much wear.

• The implement electronic control module is not calibrated.

• The pilot relief valve is faulty.

• The main control valve is contaminated or damaged.

• The load check valve is not closing because the spring is weak or broken or because there is dirt or debris in the check valve.

• There is air in the hydraulic oil.

Note: A problem with air in the hydraulic oil must be corrected before the hydraulic system will operate at normal temperatures. There are two conditions that cause air to be in the hydraulic oil:

• Return oil is flowing into the hydraulic tank above the level of oil that is in the tank.

• There are leaks in the oil suction line between the pump and the tank.

Problem 10: There is too much lift cylinder drift.

• The control current to the solenoid is incorrect.

• The components of the main control valve are worn or damaged.

• The piston seals and/or the lift cylinders are worn.

• The load check valve is not closing because the spring is weak or broken, or because there is dirt or debris in the check valve.

Probable causes:

Problem 11: The hydraulic force is too low when the tilt control lever is moved to TILT BACK or to TILT FORWARD.

Probable causes:

• The machine is being operated improperly.

• The position sensor for the tilt control lever is sending an incorrect signal.

• The control current to the solenoid is incorrect.

• The pilot relief valve setting is too low or the valve is faulty.

• The settings of the line relief valves are too low.

• The piston seals and/or the tilt cylinder is worn.

• The main control valve is contaminated or damaged.

• The pilot control actuator is contaminated or damaged.

• The main relief setting is too low.

Problem 12: The lift cylinder will collapse or the blade will not raise when the control is in the Raised operation.

Probable causes:

• The lift control lever and/or the position sensor may be worn or damaged.

• The control current to the solenoid is incorrect.

• The pilot relief valve is faulty.

• The piston seals and/or the lift cylinders are worn.

• The main control valve is contaminated or damaged.

• The makeup valve is sticking.

• The load check valve is not closing because the spring is weak or broken, or because there is dirt or debris in the check valve.

Problem 13: There is low power to the implements.

Probable causes:

• The machine is being operated above the intended capacity.

• The engine power is too low.

• The pump has too much wear.

• The control current to the solenoid is incorrect.

• The implement electronic control system is not calibrated correctly.

• The pilot relief valve setting is too low or the valve is faulty.

• The main relief valve setting is too low.

• The settings of the line relief valves are too low.

• The piston seals and/or the cylinders are worn.

• The load check valve is damaged or contaminated.

• A solenoid on the pilot control actuator is faulty.

Problem 14: There is too much tilt cylinder drift.

Probable causes:

• The control current to the solenoid is incorrect.

• The setting of the line relief valve is too low.

• The piston seals and/or the tilt cylinder is worn.

• The components of the main control valve are worn or damaged.

• The load check valve is contaminated or damaged.

Problem 15: The tilt cylinders collapse during the tilt function.

Probable causes:

• The control current to the solenoid is incorrect.

• The setting of the line relief valve is too low.

• The piston seals and/or the tilt cylinder is worn.

• There is dirt or debris in the main control valve.

• The main control valve spool and mating surfaces may be worn or damaged.

• The makeup valve is sticking.

Problem 16: One implement function is sluggish or nonfunctional.

Probable causes:

• The position sensor for the control lever is sending an incorrect signal.

• The control current to the solenoid is incorrect.

• The setting of the line relief valve is too low.

• The main control valve spool and the mating surfaces are worn or damaged.

• A pilot control actuator is sticking.

Problem 17: The implements are not functioning.

Probable causes:

• The implement lockout switch is in the LOCKED position.

• The solenoid in the pilot supply combination valve is faulty.

• The element in a fuse has separated.

• The pilot and braking pump is worn or damaged.

• The main hydraulic pump has too much wear.

• The pilot relief valve setting is too low or the valve is faulty.

• The main relief valve setting is too low.

• The implement electronic control module has failed.