Case 1840 Loader Troubleshooting Hydraulic and Drive System Failures

[MikePhua]

The Case 1840 and Its Role in Skid Steer Evolution
The Case 1840 skid steer loader was introduced in the early 1990s as part of Case Construction Equipment’s push to dominate the compact loader market. With a rated operating capacity of 1,400 lbs and a robust mechanical design, the 1840 quickly became a favorite among contractors, landscapers, and farmers. Its popularity stemmed from its simplicity, reliability, and ease of service—qualities that helped Case sell tens of thousands of units across North America and beyond.
Case, founded in 1842 and merged with New Holland under CNH Industrial, has long been known for its durable earthmoving equipment. The 1840 was powered by a naturally aspirated 51 hp Cummins 4B diesel engine, paired with a hydrostatic drive system and chain-driven final drives. Its mechanical controls and analog gauges made it easy to operate and repair, even in remote or rugged environments.
Common Symptoms of Operational Failure
Operators of aging Case 1840 units often encounter a range of issues that can render the machine inoperable or sluggish. Typical symptoms include:

• Loader arms and bucket failing to respond
  
• Machine unable to move forward or reverse
  
• Hydraulic whine or cavitation noise
  
• Sudden loss of drive power after warm-up
  
• Fluid leaks around pump or control valve
  

A contractor in Alberta reported that his 1840 would start and idle normally, but after 10 minutes of operation, the loader arms stopped responding and the machine refused to move. After a series of tests, the issue was traced to a failing charge pump and contaminated hydraulic fluid.
Hydraulic System Diagnosis and Pressure Testing
The 1840’s hydraulic system is built around a gear-type charge pump feeding two hydrostatic pumps—one for each drive motor. The loader lift and tilt functions are controlled by a separate valve block powered by the same reservoir. When hydraulic performance drops, the following steps are recommended:

• Check hydraulic fluid level and condition
  
• Inspect suction and return filters for clogging
  
• Test charge pump pressure (should exceed 250 psi at idle)
  
• Examine control valve spools for sticking or wear
  
• Verify relief valve settings and bypass flow
  

If the charge pump fails to build pressure, the hydrostatic pumps will not engage, and loader functions will become erratic. Contaminated fluid can also cause spool valves to stick, leading to intermittent control loss.
A technician in Chile replaced the charge pump on a 1840 after discovering metal shavings in the filter housing. The new pump restored full hydraulic function, and the machine returned to service after a complete system flush.
Drive System and Chain Case Inspection
The Case 1840 uses a chain-driven final drive system housed in sealed compartments on each side of the loader. These chains transfer power from the hydrostatic motors to the wheels. Common drive issues include:

• Chain tension loss due to wear or broken links
  
• Sprocket misalignment or bearing failure
  
• Hydrostatic motor cavitation from low fluid pressure
  
• Drive control linkage misadjustment
  

To diagnose drive failure:

• Inspect chain case fluid level and condition
  
• Check for chain slack or excessive noise during travel
  
• Test hydrostatic motor output pressure
  
• Verify control lever travel and neutral position calibration
  

A fleet manager in Texas rebuilt the chain case on two 1840 units after noticing jerky movement and grinding noise. The chains had stretched beyond spec, and the sprockets showed uneven wear. After replacement and realignment, both machines operated smoothly.
Electrical and Safety Interlock Considerations
Though largely mechanical, the 1840 includes basic electrical systems for ignition, lighting, and safety interlocks. These systems can prevent operation if faults are present. Key components include:

• Seat switch and lap bar interlock
  
• Neutral start switch on control levers
  
• Battery voltage and ground integrity
  
• Starter solenoid and relay function
  

If the machine powers on but fails to engage hydraulics or drive, check:

• Seat switch continuity and lap bar engagement
  
• Neutral start switch alignment
  
• Battery voltage (should exceed 12.4V resting)
  
• Starter relay click and solenoid response
  

A restorer in Ontario bypassed a faulty seat switch temporarily to diagnose a no-drive condition. Once confirmed, he replaced the switch and restored full interlock functionality.
Preventive Maintenance and Long-Term Reliability
To keep the Case 1840 running reliably:

• Change hydraulic fluid and filters every 500 hours
  
• Inspect chain case oil and tension quarterly
  
• Grease all pivot points and loader arms weekly
  
• Monitor control linkage wear and adjust annually
  
• Flush system after any major component failure
  

Recommended fluids:

• Hydraulic: ISO 46 or Case HY-TRAN equivalent
  
• Chain case: SAE 80W-90 gear oil
  
• Engine: SAE 15W-40 diesel-rated oil
  

A technician in Florida added a magnetic drain plug to his chain case and hydraulic reservoir. This helped capture fine metal particles and allowed early detection of wear trends.
Conclusion and Recommendations
The Case 1840 remains a dependable skid steer loader when maintained properly. Its mechanical simplicity makes it ideal for field repairs, but aging components—especially in the hydraulic and drive systems—require close attention.
Recommendations include:

• Test charge pump pressure during warm-up to detect early failure
  
• Flush hydraulic system after contamination or pump replacement
  
• Inspect chain case for wear and maintain proper tension
  
• Verify safety interlocks and control linkage calibration
  
• Document service intervals and monitor fluid condition regularly
  

With disciplined maintenance and informed troubleshooting, the Case 1840 continues to lift, grade, and haul with the rugged reliability that made it a staple in compact equipment fleets worldwide.