STRIP 8S6851 - Caterpillar

Sudden movement of the machine or release of oil under pressure can cause injury to persons on or near the machine.To prevent possible injury, perform the procedure that follows before testing and adjusting the power train.
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.
Care must be taken to ensure that fluids are contained during performance of inspection, maintenance, testing, adjusting and repair of the machine. Be prepared to collect the fluid with suitable containers before opening any compartment or disassembling any component containing fluids.Refer to Special Publication, NENG2500, "Caterpillar Tools and Shop Products Guide", for tools and supplies suitable to collect and contain fluids in Caterpillar machines.Dispose of all fluids according to local regulations and mandates.
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.Probable Causes of Problems in the Propel System
ProblemThe propel system does not operate in either direction.Probable Cause
The parking brake switch has failed.
The cable for propel control is loose.
The cable for propel control has failed.
The DA valve has failed.
The piston seals in the brake assemblies are worn or damaged.
The brake solenoid valve has failed.
The needle valve for the manual brake release is closed.
The electrical circuit contains a fault.
The brake relay has failed.
Charge pressure is low.ProblemThe propel system operates in one direction only.Probable Cause
The pump servo piston has failed.
The flushing valve is sticking in one direction.
The charge check valve in the main relief valve has failed.
One of the main relief valves is set in position for towing bypass.
The main relief valve in the high pressure loop is damaged or incorrectly adjusted.ProblemThe propel system does not disengage when the propel control lever is returned to NEUTRAL.Probable Cause
The pump servo piston has failed.
The propel cable is improperly adjusted.
The adjustment for the servo piston is incorrect.
The adjustment of the swashplate to NEUTRAL is incorrect.ProblemThe charge pressure is low in NEUTRAL.Probable Cause
The hydraulic oil level is low.
The charge filter is plugged.
The charge relief valve is contaminated with debris, or the charge relief valve is faulty.
The charge pump in the propel pump is faulty.
A propel motor has excessive internal leakage.
The strainer in the hydraulic tank is plugged.
There is excessive leakage in the case drain for the propel pump.ProblemThe charge pressure is low while the machine is moving.Probable Cause
A propel motor has excessive internal leakage.
The flushing relief valve is contaminated with debris, or the flushing relief valve is faulty.
A propel motor has excessive internal leakage.ProblemThe brakes do not release when the parking