History

• International introduced the 6.0L as a replacement for the dirty and fuel-hungry 7.3L. The 6.0L utilized a number of features and emerging technologies not found on earlier designs.
  
  

Basic Problem

• The 6.0L's primary design consideration was that it should run cleanly and efficiently at cruise RPM; it did, but idle quality suffered by design. While idling, the 6.0L tended to produce a great deal of soot and other noxious emissions.
  
  

Complications

• Soot clogged not only the turbocharger's variable vanes (resulting in loss of performance), but the EGR (exhaust gas recirculation) port. A clogged EGR port led to turbo overspeeding and overboosting, resulting in a lean (fuel-poor) condition and combustion chamber pressure spikes.
  
  

End Result

• These pressure spikes put excess stress on the 6.0L's torque-to-yield (TTY) head bolts, which were designed to permanently stretch when torqued. The weak TTY bolts would stretch even further rather than absorb the stress, leading to blown head gaskets and engine failure.