Volvo L110H Park Brake and Cooling System Failures

[MikePhua]

The Volvo L110H Loader Lineage
The Volvo L110H is part of the H-series wheel loaders, introduced by Volvo Construction Equipment in the mid-2010s as a successor to the G-series. Volvo CE, founded in 1832 and headquartered in Sweden, has long been a pioneer in construction machinery, known for innovations in operator comfort, fuel efficiency, and hydraulic control. The L110H was designed for mid-range loading tasks, offering a balance between power and maneuverability. It features a 6-cylinder Volvo D8J engine producing approximately 256 horsepower, a load-sensing hydraulic system, and an advanced cooling package.
Sales of the L110H have been strong across Europe and North America, with thousands of units deployed in quarrying, forestry, and municipal operations. Its popularity stems from its fuel-efficient engine, comfortable cab, and smart electronics—but like any machine, it’s not immune to system failures.
Symptoms of Brake and Cooling Malfunctions
Operators have reported a combination of issues on the L110H that include:

• Low brake pressure on startup (around 90 bar)
  
• Brake pressure rising only when hydraulic functions are engaged (up to 160 bar during bucket curl)
  
• Fan speed remaining low at idle (250 rpm) and maxing out at only 700 rpm under full engine load
  
• Cooling system unable to maintain optimal temperature, triggering fault codes
  

These symptoms suggest a deeper issue within the hydraulic and cooling subsystems, particularly involving the third hydraulic pump (commonly referred to as P3).
Understanding Hydraulic Pump Functionality
The L110H uses a multi-pump hydraulic system:

• P1 and P2 handle primary functions like lift, tilt, and steering
  
• P3 supports auxiliary systems including brake charging and cooling fan drive
  

Each pump is controlled by a proportional pulse-width modulation (PWM) valve, which adjusts displacement based on demand. If P3 fails or its PWM valve malfunctions, the result is insufficient flow to the brake accumulator and fan motor.
Terminology annotation:

• PWM Valve: An electronically controlled valve that modulates hydraulic flow using pulse-width signals.
  
• Brake Accumulator: A pressurized vessel that stores hydraulic energy to ensure consistent brake pressure.
  
• Displacement: The volume of fluid a pump moves per revolution, affecting system pressure and flow.
  

Diagnostic Strategy and Field Testing
To confirm pump failure, technicians can perform the following steps:

• Disconnect the PWM valve on P3. If the pump responds with full displacement, the valve is likely faulty.
  
• If no change occurs, the pump itself may be seized or internally damaged.
  
• Use pressure gauges to monitor brake circuit and fan motor pressures under various operating conditions.
  
• Check for hydraulic fluid contamination, which can cause valve sticking or pump scoring.
  

In one documented case, a Romanian contractor observed brake pressure rising only when the bucket was curled—indicating that P1 or P2 were compensating for P3’s failure. This workaround is unsustainable, as it overloads the primary pumps and risks further system degradation.
Cooling System Implications
The cooling fan on the L110H is hydraulically driven and speed-controlled based on engine temperature and load. If P3 fails, the fan receives insufficient flow, leading to overheating. This can trigger derate modes, reduce engine performance, and in extreme cases, cause head gasket failure or turbocharger damage.
A similar incident occurred in Illinois, where a fleet operator noticed repeated overheating on multiple H-series loaders. After replacing the PWM valves and flushing the hydraulic system, normal fan speeds were restored, and brake pressure stabilized.
Preventative Measures and Recommendations
To avoid recurrence of these issues, operators and maintenance teams should:

• Monitor brake pressure during startup and idle—normal values should exceed 120 bar
  
• Log fan speed data during operation; speeds below 800 rpm under load may indicate flow restriction
  
• Replace hydraulic filters at recommended intervals and inspect for metallic debris
  
• Use OEM diagnostic software to check PWM valve signals and pump displacement feedback
  
• Consider installing inline flow meters for real-time hydraulic monitoring
  

If pump replacement is necessary, ensure that the new unit is calibrated and flushed into a clean system. Replacing only the pump without addressing contamination or valve faults may lead to rapid failure.
Conclusion
The Volvo L110H is a robust and capable machine, but its reliance on electronically modulated hydraulics means that failures in one subsystem can cascade into others. Brake pressure and cooling fan issues often trace back to pump P3 and its associated control valve. With proper diagnostics, timely intervention, and preventative maintenance, these problems can be resolved before they compromise safety or productivity. The lesson is clear: in modern loaders, hydraulic health is central to operational integrity.