FILM-CATERPILLAR 2017719 - Caterpillar

Probable Causes
Contamination of the hydraulic system oil
Insufficient pressure oil to the brakes
Charge system pressure is not correct.
Failed brake components
The brake solenoid valve is not functioning properly.Recommended Actions
Escaping fluid under pressure, even a pinhole size leak, can penetrate body tissue, causing 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.
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, "Caterpillar Dealer Service Tool Catalog" for tools and supplies suitable to collect and contain fluids on Caterpillar products.Dispose of all fluids according to local regulations and mandates.
Follow this procedure if the machine does not move or if the machine moves slowly.Initially, ensure that the symptom is active. If the symptom is intermittent then a probable cause is oil contamination.Next, a check of the brake pressure guides the diagnosis of the problem to the brake system or to the hydrostatic transmission.If the brake pressure is correct then the hydraulic system is eliminated as the probable cause of the problem. The electrical system is also eliminated as the probable cause of the problem. Thus, sufficient pressure is sent to the brake in order to release the brake. Therefore, an issue in the hydrostatic transmission is the probable cause.If the brake pressure is not correct then the hydraulic system or the electrical system is the probable cause of the problem. Next, a check of the system pressure determines if the system pressure is high enough. The system pressure allows the brake solenoid to supply sufficient pressure to the brakes.If the charge system pressure is correct then check the brake solenoid valve. If the brake release pressure is correct then a mechanical problem may exist. If the brake release pressure is low then there could be a problem in the charge system. This check guides the diagnosis of the problem to the brake control valve or to the brakes.Contamination Of The Hydraulic System Oil
If the symptom is not active or if the symptom is intermittent, oil contamination may be the problem.Remove any contaminants from the oil by filtering the oil that is used in the machine.Change the hydrostatic transmission and hydraulic system oil. Change the oil filter element and clean the screens. Refer to Operation and Maintenance Manual, "Hydraulic System Oil - Change" for the 953D and the 963D machines. Refer to Operation and Maintenance Manual, "Hydrostate Transmission and Hydraulic System Oil - Change" for the 973D machines.Insufficient Pressure Oil To The Brakes
The brakes are engaged by spring force. The brakes are released by pressure oil which is sent from the control solenoid to the brakes. Therefore, insufficient pressure oil to the brakes is a probable cause of the symptom.Charge System Pressure