Volvo L350F exhaust valve spring failure after overhaul

[MikePhua]

Summary
A Volvo L350F wheel loader experienced catastrophic failure of eight outer exhaust valve springs just 100 hours after a full engine overhaul. The incident highlights the importance of updated components, correct valve lash settings, and awareness of design variations in rocker arms and valve bridges.
Volvo L350F background and engine architecture
The Volvo L350F is a flagship wheel loader introduced in the late 2000s, designed for heavy-duty mining, quarrying, and bulk material handling. Powered by a Volvo D16 engine—a 16-liter inline-six turbo diesel—it delivers over 530 horsepower and is known for its torque-rich performance and fuel efficiency. Volvo Construction Equipment, founded in 1832, has consistently led innovation in loader design, with the L350F representing one of its most powerful and refined models.
The D16 engine uses a dual-spring valve system with inner and outer springs to ensure valve stability under high load and temperature. The exhaust side is particularly stressed due to elevated thermal cycling and backpressure from emissions systems like I-EGR (Internal Exhaust Gas Recirculation).
Failure symptoms and initial findings
Operators reported a ticking noise during operation. Upon inspection, eight outer exhaust valve springs were found broken, though the inner springs had kept the valves seated. The engine had recently undergone a full rebuild, including new rocker shafts, bridges, and springs. The camshaft was reused, and the overhaul was performed by a reputable machine shop.
Possible causes of spring failure
Several contributing factors were identified:

• Incorrect valve lash: If lash is set too tight, springs may experience coil bind—where the coils compress fully and cannot absorb further motion—leading to fracture.
  
• Outdated spring design: Volvo issued updated valve springs for D13 and D16 engines years ago. Using older stock may result in premature failure.
  
• Bridge style mismatch: The engine used T-style valve bridges with pins, which require different spring specifications due to altered geometry and preload.
  
• Dust contamination: The original engine was “dusted,” meaning fine particulate entered the intake, causing accelerated wear. This may have compromised rocker geometry or valve seating.
  

Inspection and repair strategy
Technicians disassembled the rocker arms and inspected the slave pistons within the I-EGR double rockers. These pistons, which adjust lash via threaded spanner caps, were found intact with factory peening marks. However, it was recommended to:

• Remove and clean each piston
  
• Reassemble with bearing grease
  
• Peen the threads to prevent backing off
  
• Verify spanner cap torque and alignment
  

The head was removed and sent back to the rebuilder for warranty evaluation. Updated bulletins from Volvo were consulted to confirm spring compatibility with the T-style bridges.
Lessons from the field
One mechanic recalled a similar failure on a D13 engine where outdated springs were installed despite a known update. The dealership had sold old stock without verifying compatibility. Another technician emphasized the importance of floating valve bridges, which reduce stress on springs and improve longevity.
Recommendations for future rebuilds

• Always check for updated part numbers and service bulletins
  
• Confirm bridge style before selecting springs
  
• Use floating bridges when possible
  
• Set valve lash precisely using manufacturer tools
  
• Avoid reusing cams unless fully inspected for wear
  
• Replace springs in matched sets, even if only one fails
  

Conclusion
The Volvo L350F valve spring failure underscores the complexity of modern diesel engine rebuilds. With emissions systems, updated components, and multiple bridge styles in circulation, rebuilders must stay current with manufacturer guidance. A single oversight—such as using outdated springs—can lead to costly downtime and repeat repairs. Vigilance, documentation, and component compatibility are essential for reliable engine performance.