D5R2 and D6R2 Track-Type Tractors Brake Does Not Release Caterpillar

Before you complete any procedure, read Troubleshooting, "Machine Preparation for Troubleshooting" and Troubleshooting, "Visual Inspection" in this module.

Probable Cause

• Neutral default strategy

• Contamination of the hydraulic system oil

• Insufficient pressure oil to the brakes

• Transmission drag

• Insufficient system pressure

• Failed brake components

• Brake control valve

• Proportional solenoid valve

Recommended Actions

Follow this procedure if the machine does not move or if the machine moves slowly.

Neutral Default Strategy

Neutral Default Strategy is programmed in the software for the transmission to engage the service brakes on the machine under certain conditions. Neutral Default Strategy will automatically apply the service brakes for 10 seconds for the power train to stabilize during the start-up of the machine.

ReferenceFor D5R2 models refer to Specifications, Systems Operation/Testing and Adjusting, UENR4119, "Transmission".

ReferenceFor D6R2 models refer to Specifications, Systems Operation/Testing and Adjusting, UENR4109, "Transmission".

Contamination Of The Hydraulic System Oil

1. Determine that the symptom is active.

   If the symptom is intermittent, then a probable cause is oil contamination.

2. Complete this procedure only if the symptom is active.

   Results

   • ACTIVE: Proceed to "Insufficient Pressure Oil To The Brakes".

   • NOT ACTIVE: If the symptom is not active, oil contamination may be the problem. Change the power train oil. Change the oil filter element and clean the screens.

   • Stop.

Insufficient Pressure Oil To The Brakes

1. Check the brake pressure.

   The brakes are engaged by spring force. The brakes are released by pressure oil which is sent from the steering clutch and brake control valve to the brakes. Therefore, insufficient pressure oil to the brakes is a probable cause of the symptom.
   

   ReferenceFor D5R2 models refer to Specifications, Systems Operation/Testing and Adjusting, UENR4119, "Steering Clutch and Brake Pressure - Test".

   ReferenceFor D6R2 models refer to Specifications, Systems Operation/Testing and Adjusting, UENR4109, "Steering Clutch and Brake Pressure - Test".

   Expected Results

   • The pressure is correct.

   Results

   • OKAY: The pressure is correct. Proceed to "Transmission Drag".

   • NOT OKAY: The pressure is not correct. Proceed to "Insufficient System Pressure".

Transmission Drag

ReferenceFor D5R2 models refer to Specifications, Systems Operation/Testing and Adjusting, UENR4119, "Transmission Clutch Pressure - Test".

ReferenceFor D6R2 models refer to Specifications, Systems Operation/Testing and Adjusting, UENR4109, "Transmission Clutch Pressure - Test".

1. Place pressure gauges on all transmission clutches.

   1. Operate the engine.

   2. Disengage the parking brake.

   3. Press down the service brake pedal to engage the brakes.

   4. Shift through all the transmission gears.

   5. Check that the proper clutches engage for each gear.

   6. Check that the clutches disengage properly for each gear. The clutch that is disengaged should have a pressure below 137 kPa (20 psi).

      Expected Results

      • The transmission clutches engage and the transmission clutches disengage properly.

      Results

      • OKAY: The engagement of the transmission clutches was eliminated as the source of the symptom. Since the brake pressure was correct, then the brake control valve was eliminated as the cause of the symptom. Therefore, the brake is the probable cause of the symptom. Proceed to "Failed Brake Components".

      • NOT OKAY: The transmission clutches do not engage properly.

      Proceed to "The Transmission Clutch Does Not Engage" in Troubleshooting, "Transmission Clutch" in this module.

      • NOT OKAY: The Transmission Clutch Is Engaged and the Clutch Does Not Release.

      Proceed to "The Transmission Clutch Is Engaged and the Clutch Does Not Release" in Troubleshooting, "Transmission Clutch" in this module.

Insufficient System Pressure

1. Check the system pressure.
   

   ReferenceFor D5R2 models refer to Specifications, Systems Operation/Testing and Adjusting, UENR4119, "Relief Valve (Transmission) - Test and Adjust".

   ReferenceFor D6R2 models refer to Specifications, Systems Operation/Testing and Adjusting, UENR4109, "Relief Valve (Transmission) - Test and Adjust".

   Expected Results

   • The system pressure is correct.

   Results

   • OKAY: The system pressure is correct. The brake pressure is not correct. Inspect the brake control valve. Proceed to "Brake Control Valve".

   • NOT OKAY: The cause of the symptom may be the adjustment of the transmission relief valve. The transmission relief valve maintains the system pressure in the control section of the power train oil pump. Refer to Troubleshooting, "Power Train Oil Is Low" in this manual.

Failed Brake Components

1. Check the brakes.

   The brake pressure is correct and the engagement of the transmission clutches is correct. Therefore, the brakes are the probable cause of the symptom.

2. Disassemble the brakes and check the following components of the brakes for failure:
   • Brake housing

   • Reaction plate

   • Brake pistons

   • Belleville springs

   • Stationary ring gear

   • Seals

   • Splines

   • Friction discs

   • Brake plates

   • Shuttle valve

3. Replace any damaged components, if necessary.

4. Calibrate the brakes.
   

   ReferenceFor D5R2 models refer to Specifications, Systems Operation/Testing and Adjusting, UENR4119, "Calibration".

   ReferenceFor D6R2 models refer to Specifications, Systems Operation/Testing and Adjusting, UENR4109, "Calibration".

   Expected Results

   • The original symptom is resolved.

   Results

   • OKAY: The original problem is resolved.

   • Stop.

   • NOT OKAY: The cause of the problem is uncertain. Call technical support with the information that has been gathered.

Brake Control Valve

1. Disassemble the brake control valve and inspect the valve for damage.

2. Repair the components and/or replace the components, if necessary.

3. Calibrate the brakes.
   

   ReferenceFor D5R2 models refer to Specifications, Systems Operation/Testing and Adjusting, UENR4119, "Calibration".

   ReferenceFor D6R2 models refer to Specifications, Systems Operation/Testing and Adjusting, UENR4109, "Calibration".

   Expected Results

   • The original symptom is resolved.

   Results

   • OKAY: The original symptom is resolved.

   • Stop.

   • NOT OKAY: Proceed to "Proportional Solenoid Valve".

Proportional Solenoid Valve

1. Replace the proportional solenoid valve.

2. Check the operation of the machine for the original symptom.

   Expected Results

   • The original symptom is resolved.

   Results

   • OKAY: The original symptom is resolved. Calibrate the brakes.

   ReferenceFor D5R2 models refer to Specifications, Systems Operation/Testing and Adjusting, UENR4119, "Calibration".

   ReferenceFor D6R2 models refer to Specifications, Systems Operation/Testing and Adjusting, UENR4109, "Calibration".

• Stop.

• NOT OKAY: The cause of the symptom is uncertain. Call technical support with the information that has been gathered.