Torque Specifications and Engine Service Notes for the Case 590 Turbo Backhoe

[MikePhua]

The Case 590 Turbo and Its Engine Platform
The Case 590 Turbo backhoe loader, introduced in the late 1980s and continuing into the early 1990s, was a high-performance evolution of the 580 series. Designed for heavy-duty excavation, trenching, and material handling, the 590 Turbo featured a robust frame, extended reach, and a turbocharged diesel engine that delivered improved torque and responsiveness under load. The engine commonly found in these machines was the Case 4-390, a 4.5L inline-four diesel that shared architecture with the Cummins 4BT platform, though with proprietary modifications tailored to Case’s hydraulic and cooling systems.
Case Construction Equipment, a division of CNH Industrial, has a long history dating back to 1842. The 590 series was part of their push to offer more powerful and versatile backhoes for municipal and contractor fleets, and it remains a respected model in the used equipment market.
Critical Torque Values for Engine Rebuild
When performing internal engine service—such as rolling in new bearings or replacing head gaskets—accurate torque specifications are essential to ensure proper clamping force, seal integrity, and long-term reliability. The following torque values apply to the Case 4-390 engine found in the 590 Turbo:
Main Bearing Cap Bolts:

• Stage 1: 50 Nm
  
• Stage 2: 60 Nm
  
• Stage 3: 90 Nm
  
• Final: Additional 90 degrees (angle torque) with oiled threads
  

Connecting Rod Bolts:

• Stage 1: 30 Nm
  
• Stage 2: 60 Nm
  
• Final: Additional 60 degrees with oiled threads
  

Oil Pan Bolts:

• Uniform torque: 24 Nm
  

Cylinder Head Bolts:

• Stage 1: 90 Nm
  
• Stage 2: Recheck torque
  
• Stage 3: Long bolts only: 120 Nm
  
• Stage 4: Recheck torque
  
• Final: All bolts receive an additional 90 degrees with oiled threads
  

Rocker Pedestal Bolts:

• Short bolts: 24 Nm
  

Valve Clearance Settings:

• Intake: 0.25 mm cold
  
• Exhaust: 0.51 mm cold
  

Terminology annotation:
- Nm (Newton-meters): A metric unit of torque; 1 Nm ≈ 0.737 ft-lbs.
- Angle Torque: A tightening method where bolts are turned a specific number of degrees after reaching a base torque, ensuring consistent stretch.
- Oiled Threads: Threads lubricated before tightening to reduce friction and achieve accurate torque.
- Cold Clearance: Valve lash measured when the engine is at ambient temperature, ensuring proper thermal expansion during operation.
Best Practices for Assembly and Inspection
When rebuilding the Case 4-390 engine, attention to detail is critical. Torque values must be applied in sequence and verified with a calibrated torque wrench. Angle torque procedures require a degree wheel or electronic angle gauge to ensure precision.
Recommendations:

• Always clean bolt threads and mating surfaces before assembly
  
• Use assembly lube on bearings and camshaft journals
  
• Replace head bolts if they show signs of stretching or corrosion
  
• Verify oil pump clearance and prime before startup
  
• Check crankshaft end play and rod side clearance during reassembly
  

In one field case, a technician reused head bolts without checking stretch and experienced coolant seepage within 100 hours of operation. Replacing the bolts and retorquing solved the issue permanently.
Sourcing Parts and Documentation
Because the 590 Turbo predates digital service platforms, locating manuals and torque specs can be challenging. Aftermarket rebuild kits often include torque charts, and many suppliers offer downloadable PDFs upon request. For legacy machines, contacting Case dealers with the full PIN (Product Identification Number) can yield archived service data.
Suggestions:

• Record all torque values and procedures during disassembly for reference
  
• Photograph bolt patterns and component orientation
  
• Use OEM gaskets and seals to ensure compatibility with torque specs
  
• Cross-reference part numbers with Cummins 4BT where applicable, but confirm Case-specific tolerances
  

Conclusion
Servicing the Case 590 Turbo’s 4-390 engine requires precision, patience, and a clear understanding of torque procedures. With proper tools and verified specifications, technicians can restore performance and extend the life of this durable workhorse. Whether rebuilding in the field or in a shop, the key to success lies in methodical assembly and respect for the engineering that made the 590 Turbo a trusted name in heavy equipment.