Hydraulic Cavitation and Restoration Challenges on the Mauldin 3-5 Roller

[MikePhua]

The Mauldin 3-5 and Its Legacy in Compact Paving
The Mauldin 3-5 roller, produced in the mid-1980s by Mauldin Equipment, represents a class of compact vibratory rollers designed for small-scale paving, patchwork, and shoulder compaction. Mauldin, a South Carolina-based manufacturer founded in the 1960s, built its reputation on producing reliable, operator-friendly machines for municipal and contractor use. While the 3-5 model was never a high-volume seller, it found favor among crews needing maneuverable rollers with hydraulic drive and vibration systems.
The 3-5 was equipped with a hydrostatic transmission powered by a variable displacement pump—often a Sperry Vickers unit—feeding hydraulic motors on the drum and drive wheels. Its simplicity made it serviceable in the field, but age and lack of documentation now pose challenges for restoration.
Symptoms of Hydraulic Cavitation and System Cycling
A recurring issue in aging Mauldin 3-5 units is hydraulic cavitation—a condition where vapor bubbles form in the fluid due to low pressure at the pump inlet. This leads to erratic performance, noise, and potential damage to pump internals.
Typical symptoms include:

• Initial priming followed by rapid loss of pressure
  
• System engages for 5–10 seconds, then disengages repeatedly
  
• Audible whining or growling from the pump
  
• Inconsistent drive or vibration function
  
• Difficulty identifying suction and return lines due to faded markings
  

Cavitation is especially common in machines stored for long periods or operated with degraded fluid. It can also result from incorrect hose routing or clogged filters.
Understanding the Hydrostatic Circuit and Pump Behavior
The hydrostatic system in the Mauldin 3-5 relies on a variable displacement axial piston pump. These pumps adjust flow based on swashplate angle, allowing smooth speed control without gear shifts. Key components include:

• Suction line from reservoir to pump inlet
  
• Return line from motor to reservoir
  
• Charge pump to maintain positive inlet pressure
  
• Filters on both suction and return paths
  
• Relief valves to protect against overpressure
  

In older units, identifying these lines can be difficult due to missing tags or aftermarket replacements. A common mistake is reversing suction and return hoses, which causes the pump to starve and cavitate.
Diagnostic Strategy and Field Solutions
To resolve cavitation and restore function:

• Replace all hydraulic filters, including suction strainer and return cartridge
  
• Drain and flush the reservoir, removing sludge and water contamination
  
• Use ISO 46 hydraulic fluid or manufacturer-recommended equivalent
  
• Trace hose routing from reservoir to pump and confirm suction line diameter is larger
  
• Inspect fittings for air leaks, especially at the pump inlet
  
• Prime the system by manually filling the pump housing before startup
  
• Add a transparent sight tube to monitor fluid level and flow behavior
  

If the pump continues to cycle, test charge pressure using a gauge at the auxiliary port. Pressure below 100 psi may indicate a failing charge pump or blocked passage.
Sourcing Parts and Identifying the Pump
The original pump may be a Sperry Vickers TA19 or similar model, but identification is difficult without a visible nameplate. Strategies for sourcing include:

• Comparing housing shape and port layout to known Vickers models
  
• Contacting hydraulic rebuild shops with photos and measurements
  
• Using aftermarket equivalents from Eaton or Parker if dimensions match
  
• Fabricating custom brackets or adapters if mounting differs
  

One restorer in New Jersey successfully rebuilt a 3-5 by matching the pump to a surplus unit from a forklift, adapting the flange and shaft coupling to fit.
A Story from the Pavement
In 2024, a retired road crew foreman in Pennsylvania acquired a Mauldin 3-5 from a township auction. The roller had sat idle for years and exhibited classic cavitation symptoms. After replacing all hoses, flushing the tank, and installing a new suction filter, he discovered the inlet line had been reversed during a prior repair. Correcting the routing and priming the pump restored full function. The roller went on to compact asphalt patches for a local veterans’ memorial walkway.
Preventive Measures and Long-Term Reliability
To maintain hydraulic health in compact rollers:

• Label all hoses during disassembly to prevent misrouting
  
• Use high-quality fluid with anti-foam additives
  
• Install a breather cap with desiccant to reduce moisture ingress
  
• Add a magnetic drain plug to capture wear particles
  
• Perform annual fluid analysis to monitor contamination levels
  

For legacy machines like the Mauldin 3-5, documentation may be scarce, but mechanical intuition and methodical testing can overcome most obstacles.
Conclusion
The Mauldin 3-5 roller, though modest in size and vintage in design, remains a capable tool when properly maintained. Hydraulic cavitation is a silent killer of performance, but with careful diagnosis, fluid management, and hose verification, the system can be revived. In the world of compact paving, even a forgotten roller can find new life—rolling forward with pressure, precision, and pride.