Diagnosing Engine Irregularities in the John Deere 310 Backhoe

[MikePhua]

The John Deere 310 and Its Historical Significance
The John Deere 310 backhoe loader, first introduced in the early 1970s, marked a turning point in compact construction machinery. Built by Deere & Company, founded in 1837, the 310 series combined a front loader and rear excavator into a single, versatile unit. The original 310 featured a three-cylinder diesel engine, mechanical shuttle transmission, and open-center hydraulic system. It was designed for utility contractors, farmers, and municipalities needing a reliable machine for trenching, grading, and material handling.
By the mid-1970s, the 310 had become one of Deere’s best-selling backhoes, with thousands of units deployed across North America. Its reputation for mechanical simplicity and ruggedness made it a favorite among owner-operators. The three-cylinder engine, though modest in power, was praised for its fuel efficiency and cold-start reliability.
Symptoms of Engine Miss and Breather Noise
One operator reported an erratic engine miss accompanied by a rhythmic puffing sound from the breather when the valve cover was removed. This symptom resembles the behavior of an air compressor, suggesting internal pressure fluctuations within the crankcase. The injectors were tested and found to be functioning properly, ruling out fuel delivery as the primary cause.
In diesel engines, crankcase pressure anomalies often point to valve timing issues, piston ring blow-by, or cylinder imbalance. The absence of visible blow-by from the breather complicates the diagnosis, but the audible compression pulses indicate that combustion pressure may be escaping into the valve train cavity.
Valve Train Inspection and Cylinder Pressure Testing
The first step in diagnosing such issues is to inspect the valve train. Key components include:

• Push rods: These transfer motion from the camshaft to the rocker arms. Bent or misaligned rods can disrupt valve timing.
  
• Rocker arms: These pivot on a shaft and actuate the valves. Excessive wear or binding can cause uneven valve lift.
  
• Adjustment screws: These set valve lash. If one screw is significantly tighter than others, it may indicate a collapsed lifter or worn cam lobe.
  

Running the overhead—adjusting valve lash to factory specifications—did not resolve the miss, suggesting a deeper issue. A cylinder pressure test should have been performed before removing the head, as it can pinpoint compression loss due to valve leakage, head gasket failure, or piston ring wear.
Head Removal and Internal Condition
After removing the cylinder head and sending it to a machine shop, the operator noted that the engine internals were exceptionally clean. This suggests consistent oil changes and good maintenance practices. Clean pistons and liners reduce the likelihood of ring failure, but visual inspection alone cannot confirm sealing integrity.
The machine had approximately 2,800 hours—low for a 1970s-era backhoe. This supports the theory that the issue may be isolated to a single valve or cylinder rather than systemic wear.
A Story from the Field
In eastern Oregon, a truck driver turned equipment owner purchased a 1975 John Deere 310 for light excavation work. After noticing the engine miss, he pulled the injectors and sent them for testing. All passed. Frustrated, he removed the head prematurely, hoping to find a cracked valve or damaged seat. The machine shop found no major defects, leaving the operator to reassemble and continue diagnostics.
Later, he discovered that one push rod was slightly bent, likely from a previous over-rev or improper adjustment. Replacing the rod and resetting valve lash resolved the miss. The breather noise diminished, confirming that valve timing had been the culprit. The lesson: always test cylinder pressure before disassembly, and never underestimate the value of a thorough valve train inspection.
Recommendations for Diagnosing Engine Misses
For operators facing similar symptoms in older diesel engines:

• Perform a cylinder pressure test before removing the head.
  
• Inspect push rods for straightness using a flat surface and calipers.
  
• Check rocker arm freedom and shaft wear.
  
• Compare valve lash across all cylinders. Uneven adjustment may indicate deeper issues.
  
• Use a stethoscope or hose to listen for internal noises during operation.
  
• Monitor breather output for signs of blow-by or rhythmic pulsing.
  

Preventative Maintenance Tips
To extend engine life and reduce the risk of valve train issues:

• Change oil every 100–150 hours using high-detergent diesel-rated oil.
  
• Adjust valve lash annually or every 500 hours.
  
• Use fuel additives to reduce injector fouling.
  
• Keep the air filter clean to prevent dust ingestion.
  
• Warm up the engine before applying load, especially in cold climates.
  

Conclusion
The John Deere 310 remains a durable and serviceable machine, even decades after its release. Engine misses and breather noise can be challenging to diagnose, but with methodical inspection and respect for mechanical fundamentals, most issues can be resolved without major overhaul. These machines were built to last—and with a bit of patience, they still do.