CAT 315 CL Pump Noise and Vibration Analysis

[MikePhua]

CAT 315 CL Background
The CAT 315 CL is a mid-sized hydraulic excavator produced by Caterpillar, typically weighing around 15 tons with an operating engine output of 110–120 kW. Introduced in the early 2000s, the 315 CL targeted the construction and earthmoving markets, offering a combination of fuel efficiency, precision hydraulics, and reliability. Caterpillar, founded in 1925, has maintained a strong global presence, selling thousands of units annually with extensive dealer networks for maintenance and parts. The machine’s dual-pump hydraulic system allows simultaneous multi-function operation, providing efficient digging, lifting, and loading.
Pump Noise Symptoms
Owners of CAT 315 CL units with high hours, around 9,000 h, have reported grinding or vibrating noises originating from the pump side, often triggered when multiple functions operate simultaneously. Symptoms include:

• Vibration and metallic grinding sounds
  
• Intermittent loss of hydraulic responsiveness
  
• Oil appearing foamy with visible air bubbles despite proper fluid levels
  

These signs typically indicate cavitation in the hydraulic pump or contamination within the system. Cavitation occurs when air enters the pump suction line, forming bubbles that collapse under pressure, causing vibration, noise, and accelerated wear.
Common Causes
Field reports and service analysis suggest several potential causes:

• Metal contamination
  Iron particles from previous pump wear can circulate, damaging internal components and creating abrasive conditions.
  
• Air ingestion
  Loose hose clamps, clogged suction screens, or deteriorated hoses allow air to enter the hydraulic circuit, resulting in cavitation and foamy oil.
  
• Incomplete system cleaning
  Even after a pump replacement, residual debris in the tank, suction lines, or filters can continue to damage the new pump.
  
• Suction filter issues
  “Cleanout” or auxiliary filters installed to capture fine particles can clog quickly and need frequent inspection and replacement to prevent pump stress.
  

Diagnostic and Maintenance Recommendations
Effective troubleshooting involves systematic inspection:

• Inspect suction hoses and clamps for leaks or looseness
  
• Clean or replace tank suction screens and in-tank filters
  
• Monitor hydraulic oil for air bubbles or contamination
  
• Avoid operating the machine until issues are resolved to prevent pump failure
  
• Check both return and suction filters, ensuring bypass valves function properly to avoid flow restrictions
  

Preventive maintenance is critical; changing auxiliary cleanout filters weekly can protect the hydraulic pump from premature failure. Field technicians note that Cat Reman pumps are rarely faulty upon installation, so persistent issues often originate from the system inlet or residual contamination rather than the pump itself.
Practical Field Example
A Maine operator replaced a CAT 315 CL pump after detecting high iron counts in oil samples. Despite installing a reman pump with warranty coverage, the machine continued to exhibit intermittent vibration and grinding noises. Subsequent inspection revealed foamy oil, indicating cavitation caused by air ingestion through the suction line. Once the suction screen was cleaned and hose clamps tightened, normal operation resumed, illustrating the importance of system-wide cleanliness and proper air-tight connections.
Conclusion
CAT 315 CL hydraulic pump noise and vibration are commonly linked to air ingestion, residual contamination, and inadequate suction filtration. Proper preventive maintenance, including frequent filter cleaning, suction line inspection, and careful monitoring of hydraulic oil, is essential for extending pump life and ensuring reliable excavator performance. Operators should address symptoms immediately to avoid accelerated wear or catastrophic pump failure, keeping the machine fully operational for demanding construction and earthmoving tasks.