Radiator Removal and Cooling System Service on the John Deere 850J Dozer

[MikePhua]

The 850J and Its Cooling Architecture
The John Deere 850J crawler dozer was introduced in the early 2000s as part of Deere’s J-series, designed for heavy earthmoving, site prep, and forestry work. With an operating weight exceeding 40,000 lbs and powered by a 6-cylinder John Deere PowerTech engine producing up to 200 horsepower, the 850J combined brute force with electronic control and modular serviceability.
Its cooling system is engineered to handle prolonged high-load operation in dusty, high-temperature environments. The radiator is part of a multi-core assembly that includes the charge air cooler, hydraulic oil cooler, and transmission cooler. These components are stacked and shrouded to optimize airflow while minimizing debris accumulation.
Reasons for Radiator Removal
Radiator removal may be necessary due to:

• Internal clogging from scale or sediment
  
• External blockage from dust, chaff, or mud
  
• Leaks at core seams or tank joints
  
• Cracked mounting brackets or vibration damage
  
• Overheating under load despite clean fins
  

A land-clearing crew in Arkansas reported persistent overheating during summer operations. After flushing the coolant and replacing the thermostat, the issue remained. Radiator removal revealed a layer of compacted pine needles between the cores, invisible from the outside.
Preparation and Safety Protocols
Before removing the radiator:

• Park the machine on level ground and engage the parking brake
  
• Disconnect battery to prevent electrical shorts
  
• Allow engine to cool fully before draining coolant
  
• Use spill containment to capture fluid
  
• Remove engine side panels and top shroud for access
  

Tools required:

• 1/2-inch and 3/4-inch socket sets
  
• Pry bars and panel removal tools
  
• Torque wrench for reinstallation
  
• Coolant recovery container (minimum 10 gallons)
  
• Lifting straps or hoist rated for 300 lbs or more
  

Wear gloves and eye protection. Radiator fins are sharp, and coolant may contain additives harmful to skin.
Disassembly Sequence and Component Access
The radiator is mounted behind the grille and ahead of the engine block. Removal steps include:

• Disconnect upper and lower radiator hoses
  
• Remove fan shroud bolts and lift shroud clear
  
• Unbolt charge air cooler and hydraulic cooler brackets
  
• Disconnect temperature sensor wiring and fan clutch harness
  
• Remove mounting bolts at radiator base and top frame
  
• Use hoist or loader boom to lift radiator vertically
  

Take care not to damage adjacent coolers or wiring harnesses. Label all connectors and hose clamps for reassembly.
Inspection and Cleaning Recommendations
Once removed:

• Inspect core for bent fins, corrosion, or leaks
  
• Pressure test radiator to 15 psi and check for drop
  
• Flush internally with low-pressure water and radiator cleaner
  
• Use compressed air to blow out external debris from fins
  
• Straighten bent fins with a fin comb
  

If leaks are found at solder joints or tanks, consider professional recoring or replacement. Aftermarket radiators may be available, but OEM units offer better fitment and warranty support.
Reinstallation and System Priming
To reinstall:

• Lower radiator into position using guide pins or alignment marks
  
• Torque mounting bolts to spec (typically 45–60 ft-lbs)
  
• Reconnect hoses and verify clamp integrity
  
• Reinstall fan shroud and cooler brackets
  
• Reconnect electrical harnesses and sensors
  
• Fill coolant system with 50/50 mix of ethylene glycol and distilled water
  

Bleed air from the system by running engine at idle with radiator cap off until thermostat opens. Top off coolant and check for leaks.
Preventive Maintenance and Cooling System Longevity
To extend radiator life:

• Blow out fins weekly during dusty operations
  
• Flush coolant every 1,000 hours or annually
  
• Use corrosion-inhibiting coolant additives
  
• Inspect hoses and clamps monthly
  
• Monitor engine temperature via onboard diagnostics
  

Install a debris screen or reversing fan if operating in forestry or ag environments. Some operators retrofit access doors for easier cleaning between cores.
Conclusion
Radiator removal on the John Deere 850J is a labor-intensive but manageable task with the right tools and preparation. Whether addressing overheating, leaks, or performance degradation, proper disassembly, inspection, and reinstallation ensure the cooling system continues to protect the engine under extreme conditions. With regular maintenance and attention to airflow, the 850J remains a reliable powerhouse across rugged terrain and long shifts.