SERVICE AR. 3379643 - Caterpillar

Cold ambient temperatures could result in the loss of secondary braking capability due to inadequate hydraulic accumulator nitrogen pre-charge. The loss of the secondary braking system as well as the main hydraulic pressure will result in little or no braking capability and a potential for injury or death.It is recommended to perform a brake accumulator check anytime the machine has been idle for longer than two hours below −25 °C (−13 °F). Refer to Operation and Maintenance Manual before performing any check of the brake accumulator.
Pressurized System!Hydraulic accumulators contain gas and oil under high pressure. DO NOT disconnect lines or disassemble any component of a pressurized accumulator. All gas pre-charge must be removed from the accumulator as instructed by the service manual before servicing the accumulator or any accumulator component.Failure to follow the instructions and warnings could result in personal injury or death.Only use dry nitrogen gas to recharge accumulators. See your Cat dealer for special equipment and detailed information for accumulator service and charging.
Move the engine start switch to the ON position.
Illustration 1 g01257893Note: Alert indicator (1) will illuminate if the brake system is not at the normal operating pressure.
Start the engine and run the engine for one minute in order to increase the accumulator pressure. Alert indicator (1) should turn off. Stop the engine.
Apply the service brake pedal and release the service brake pedal in order to decrease the accumulator pressure. Apply the service brake pedal and release the service brake pedal for a minimum of five applications, until alert indicator (1) illuminates.
Illustration 2 g01296741
If alert indicator (1) illuminates with less than five applications of the service brake pedal, measure the nitrogen precharge pressure of accumulators (2). Consult Systems Operation, Testing and Adjusting, "Brake Accumulator - Test and Charge" for the following information:
The correct checking procedure
The correct filling procedure
The recommended pressureYour Caterpillar dealer has the appropriate tools for measuring the precharge pressure of the brake accumulators.Note: Only use dry nitrogen gas to recharge the brake accumulators.