D7 Track-Type Tractor Electrohydraulic Systems Brake Does Not Release Caterpillar

Before you complete any procedure, read "Machine Preparation for Troubleshooting" in this manual.

Probable Cause

• Contamination of the hydraulic system oil

• Insufficient pressure oil to the brakes

• 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.

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 brake control valve 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 brake control valve to the brakes. Therefore, insufficient pressure oil to the brakes is a probable cause of the symptom.

   Expected Results

   • The pressure is correct.

   Results

   • OKAY: The pressure is correct. Proceed to "Failed Brake Components".

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

Insufficient System Pressure

1. Check the system pressure.

   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 brake relief valve.

Failed Brake Components

1. Check the brakes.

   The brake pressure 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.

   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. Look for damaged o-ring seals and inspect the valve for damage.

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

3. Calibrate the brakes.

   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.

• Stop.

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