CP34 and CS34 Vibratory Soil Compactors Propel System Caterpillar

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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.

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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.

Operational Checks

Note: The checks during operation can be used to find leakage in the system. These checks can also be used to find a bad valve, a bad pump, or a bad motor. Travel speed can be used to check the condition of the propel motors and the pump.

Operate the machine in each direction and in all speeds.

• Watch the drum and the wheels.

• Starting and stopping operations should be progressive.

• The drum and the wheel rotation should be normal at all times.

• Check for noise from the pump and drive motors.

• Check for the sound of the relief valves that are opening. The opening pressures of the relief valves are given in Relief Valve (Main) - Test and Adjust and Relief Valve (Charge) - Test and Adjust of this module.

• After the travel speed of the compactor is selected, the forward and reverse motion should be identical.

Probable Causes of Problems in the Propel System

Problem

The propel system operates in one direction only.

Probable Cause

• One of the main relief valves is damaged or out of adjustment.

• The pump servo valve has failed .

• The pump servo piston has failed.

• The rocker arm section of the pump swashplate assembly has failed.

• The flushing valve spool in the propel motor is sticking or malfunction of swashplate assembly.

Problem

The propel system does not disengage when the propel control lever is returned to neutral.

Probable Cause

• The pump servo feedback mechanism has failed.

• The pump servo piston has failed.

• The swashplate is stuck in the stroked position.

• The neutral adjustment of the servo valve is incorrect.

• The neutral adjustment of the servo piston is incorrect.

• The linkage rod between the directional control valves is incorrectly adjusted.

• The neutral adjustment for the manual displacement control lever is incorrectly adjusted.

Problem

The parking brake does not release when the parking brake switch is in the OFF position.

Probable Cause

• The parking brake switch has failed.

• There is a malfunctioning piston seal in the brake group.

• The parking brake valve has failed.

• There is a fault in the electric wiring.

• The neutral start switch has failed.

• The neutral start relay has failed.

• Low charge pressure.

• The brake relay has failed.

• Failure of the steer charge pump.

Problem

The parking brake does not engage when the parking brake button is in the ON position.

Probable Cause

• The parking brake switch has failed.

• The brake relay has failed.

• The brake discs are worn.

• There is a restricted brake line.

• The parking brake valve has failed.

• There is a fault in the electrical wiring.

Problem

There are external oil leaks from either of the piston motors.

Probable Cause

• Motor case pressure is too high.

• There is a restriction in the oil return line to the hydraulic oil tank.

• There are damaged seals due to pressure peaks, use of unapproved hydraulic oil, or an incorrect tightening torque.

• The bypass check valve in the propel pump is faulty.

Problem

The oil in the propel system overheats.

Probable Cause

• An incorrect type of oil is used in the hydraulic circuit.

• The oil cooler is internally restricted.

• The air flow through the radiator and/or the oil cooler is reduced.

• System operating at elevated pressure due to driveline mechanical failures.

• The flushing valve in a propel motor has failed.

• The bypass check valve in the propel pump has a malfunction.

• Ambient temperature is above the specification.

Problem

There is a noise in the drive motors.

Probable Cause

• There is air in the hydraulic oil.

• The retaining bolts are loose.

• The shaft bearings are bad in the motor.

• There is an inadequate pressure from the charge pump.

• There are worn gears in the drum drive box.

Problem

The pressures for the main relief valves are incorrect.

Probable Cause

• Charge pressure is low.

• The shuttle valve or the relief valve in the flushing manifold is stuck.

• There is internal damage to the propel motors.

• The rear axle assembly or the components of the drum drive are possibly damaged.