Hydraulics Leaking Down on Bobcat 753: Diagnosis and Solutions

[MikePhua]

Introduction
This article addresses the common issue of hydraulics leaking down on the Bobcat 753 skid-steer loader. When the hydraulics leak down, it can result in a loss of lifting capacity and reduced efficiency, leading to frustration for operators. Identifying the source of the leak and taking corrective action is crucial for restoring optimal performance.
Symptoms of Hydraulic Leak Down

• Slow or Jerky Movements: The hydraulic boom, bucket, or other attachments may move slowly or jerk while being operated.
  
• Lowering of the Lift Arms: The most obvious symptom is the slow or uncontrolled lowering of the lift arms or attachments even when the joystick is in the neutral or lifted position.
  
• Loss of Load Holding: If the machine struggles to hold heavy loads or slowly drifts back to the ground after lifting, it's a sign of hydraulic fluid leakage or pressure loss.
  
• Fluid Leaks: Visible signs of hydraulic fluid leaking around hoses, cylinders, or other hydraulic components.
  

Common Causes of Hydraulic Leak Down

• Worn Seals in Cylinders: One of the most common causes of hydraulic leak down is worn seals in the hydraulic cylinders. Over time, seals can degrade, allowing hydraulic fluid to bypass, causing the boom or bucket to lower when it should remain lifted.
  
• Faulty Control Valve: A malfunctioning control valve can cause hydraulic fluid to bleed off when it shouldn't, leading to slow movement or unintentional lowering of attachments.
  
• Internal Leaks in Hydraulic Pump: If the hydraulic pump is worn or malfunctioning, it may fail to maintain consistent pressure, leading to hydraulic systems not holding load or lowering unexpectedly.
  
• Damaged Hoses or Fittings: Cracked or damaged hydraulic hoses or fittings can cause fluid loss and decreased hydraulic performance.
  
• Hydraulic Fluid Contamination: Contaminated hydraulic fluid can cause blockages or interfere with the normal operation of the hydraulic system, leading to leaks or decreased efficiency.
  

Troubleshooting Steps

1. Inspect Hydraulic Cylinders and Seals: Examine the hydraulic cylinders for signs of fluid leakage. If seals appear damaged, they may need to be replaced. This is a common cause of hydraulics leaking down.
   
2. Check for External Leaks: Inspect all hydraulic hoses, fittings, and connections for visible signs of leaks. Tighten loose fittings or replace damaged hoses.
   
3. Test the Control Valve: Operate the machine and check if the control valve is malfunctioning by listening for any unusual sounds or noticing inconsistent movement in the hydraulic system. If the control valve is faulty, it may need to be rebuilt or replaced.
   
4. Check Hydraulic Fluid Levels and Quality: Ensure that the hydraulic fluid levels are within the proper range. Also, check for signs of contamination in the fluid. If contamination is detected, perform a fluid change and clean the system.
   
5. Examine the Hydraulic Pump: If other causes have been ruled out, test the hydraulic pump's pressure output. A weak or inconsistent pump could be the reason for inadequate load-holding and slow hydraulic response.
   

Solutions and Repairs

• Replace Worn Seals: If the hydraulic cylinders are leaking due to worn seals, the seals should be replaced, and the cylinders reassembled.
  
• Repair or Replace the Control Valve: A faulty control valve will need to be repaired or replaced to ensure proper hydraulic flow and pressure regulation.
  
• Fix Damaged Hoses and Fittings: Replace any cracked or leaking hoses and fittings, ensuring a secure and tight connection.
  
• Flush and Refill the Hydraulic System: After replacing fluid, flush the system to ensure all contaminants are removed, and refill with the correct hydraulic oil as recommended by the manufacturer.
  
• Replace or Rebuild the Hydraulic Pump: If the hydraulic pump is malfunctioning, it may need to be replaced or rebuilt to restore pressure and performance.
  

Conclusion
Hydraulic leak down on the Bobcat 753 is often caused by worn seals, damaged components, or fluid issues. Timely diagnosis and repairs, such as replacing seals, hoses, or fixing the control valve, are essential for restoring optimal hydraulic performance. Regular maintenance and inspections of the hydraulic system can help prevent such issues from recurring, ensuring the machine remains efficient and reliable.