3176C, 3406E and 3456 Industrial Engines Troubleshooting – Coolant Contains Fuel

Probable Causes


  • Injector sleeve or injector sleeve seal 

Recommended Actions

Injector Sleeve or Injector Sleeve Seals


  1. Remove the valve mechanism covers.


  1. Remove the fuel injectors from the cylinder head.Refer to the Disassembly and Assembly manual for details.
  1. Pressurize the cooling system in order to identify the injector sleeve that is leaking. Closely inspect the sealing joint around the top of the injector sleeve. Small amounts of coolant will be dripping from the injector sleeve that is leaking.Note: Do not allow the pressure on the cooling system to exceed 103 kPa (15 psi) during the test. Damage to the cooling system may result from applying excessive pressure.

    Refer to the Systems Operation/Testing and Adjusting manual for details.


  1. Remove the injector sleeve that is leaking. Carefully inspect the sleeve for damage. If there are visible signs of damage to the injector sleeve, replace the sleeve. Replace the O-ring seals for the injector sleeve and reinstall the sleeve. Replace any damaged components.Note: Coolant may also be contaminating the fuel system. After the engine is shutdown, the retention of pressure in the cooling system may cause the transfer of coolant into the fuel system. Visually inspect the fuel tank for coolant. The contamination of coolant in the fuel system may cause damage to injectors and other fuel system components. Ensure that all of the fuel system components are in good repair prior to returning the engine to service.


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