Hydraulic Filter and Flow Issues in the John Deere 310 Radial Pump System

[MikePhua]

The John Deere 310 and Its Hydraulic Architecture
The John Deere 310 backhoe loader series has been a cornerstone of compact construction equipment since its introduction in the early 1970s. Designed for versatility and durability, the 310 quickly gained popularity among contractors, municipalities, and farmers. With thousands of units sold across North America, the 310 evolved through multiple generations, including the 310A, B, C, D, and beyond. The 1973 model, in particular, featured a radial piston hydraulic pump—a design known for high-pressure output and compact form.
Radial piston pumps operate by using pistons arranged radially around a central shaft. As the shaft rotates, the pistons move in and out, pressurizing hydraulic fluid. This design offers excellent efficiency and durability but requires clean fluid and proper filtration to maintain performance.
Terminology Note

• Radial Piston Pump: A hydraulic pump with pistons arranged in a circle around a drive shaft, known for high-pressure capability.
  
• Hydraulic Filter: A component that removes contaminants from hydraulic fluid to protect valves, cylinders, and pumps.
  
• Control Block: A manifold containing valves and passages that direct hydraulic flow to various functions.
  
• Screen Filter: A coarse mesh filter typically located in suction lines or reservoirs to catch large debris.
  

Symptoms of Restricted Hydraulic Flow
Operators of older 310 models often report sluggish movement in specific functions, such as:

• Slow boom lift when fully extended
  
• Hesitation during high-reach operations
  
• Reduced digging force under load
  
• Delayed response in swing or bucket curl
  

These symptoms typically point to restricted hydraulic flow, which may stem from:

• Clogged suction screen in the transmission housing
  
• Dirty or collapsed hydraulic filter
  
• Internal leakage in control valves
  
• Debris accumulation in the pump’s control block
  

In one documented case, a 310 backhoe showed improved digging performance after the suction screen was cleaned, but still struggled with boom lift. This led to further investigation into the radial pump’s internal screen and control block passages.
Locating and Servicing the Radial Pump Filter
Unlike cartridge-style filters mounted externally, the radial pump in the 310 may contain an internal screen or mesh filter located within the control block. This screen is designed to catch fine debris before fluid enters the pump’s high-pressure chambers.
Steps for inspection:

• Shut down the machine and relieve hydraulic pressure
  
• Remove access panels to expose the pump and control block
  
• Locate the screen port, typically near the inlet side of the pump
  
• Extract the screen using needle-nose pliers or a magnet
  
• Clean with solvent and compressed air, inspecting for metal shavings or sludge
  

If the screen is damaged or missing, replacement is recommended. A technician in Ontario found that a missing screen allowed debris to score the pump pistons, leading to reduced output and eventual pump failure.
Hydraulic Filter Maintenance and Replacement
The 310 uses both suction and pressure-side filtration. The suction screen protects the pump from large debris, while the hydraulic filter—often mounted near the reservoir or valve block—removes finer particles.
Best practices:

• Replace hydraulic filter every 500 hours or annually
  
• Use OEM or high-quality aftermarket filters rated for 10–25 micron filtration
  
• Inspect filter housing for cracks or seal damage
  
• Monitor fluid color and viscosity during service
  

A contractor in Georgia reported that switching to synthetic hydraulic fluid and upgrading to a higher-capacity filter reduced wear on control valves and improved cold-weather performance.
Control Block Contamination and Flow Disruption
The control block on the radial pump contains multiple passages and spool valves. Over time, these can become obstructed by varnish, metal particles, or degraded seals.
Symptoms of control block issues:

• Inconsistent function response
  
• Jerky movement in boom or dipper
  
• Audible hissing or cavitation sounds
  
• Heat buildup near valve body
  

Solutions:

• Remove and disassemble the control block
  
• Clean all passages with solvent and brushes
  
• Replace worn O-rings and seals
  
• Lap spool surfaces if scoring is present
  

A rebuild shop in Texas found that 40% of flow issues in older 310 units were linked to control block contamination rather than pump failure.
Operator Stories and Practical Advice
A landowner in Wisconsin restored his 1973 310 after noticing weak boom lift. After cleaning the suction screen and replacing the hydraulic filter, performance improved slightly. He then located and cleaned the internal screen in the radial pump’s control block, which was partially blocked by sludge. The machine regained full lifting power and operated reliably through the season.
Meanwhile, a technician in British Columbia rebuilt a radial pump after discovering that the internal screen had collapsed and allowed debris into the piston chamber. He installed a new screen, flushed the system, and replaced the fluid with a high-grade synthetic blend. The pump ran smoothly for another 1,200 hours.
Conclusion
Hydraulic flow issues in the John Deere 310—especially those involving the radial piston pump—often stem from overlooked filtration components. While cleaning the suction screen and replacing the hydraulic filter are essential first steps, the internal screen within the pump’s control block plays a critical role in protecting high-pressure components. With proper inspection, cleaning, and fluid maintenance, operators can restore full hydraulic performance and extend the life of their equipment. The 310 remains a reliable workhorse, provided its hydraulic system is kept clean and well-serviced.