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

Probable Causes

Cooling System


  • Leaks in the cooling system 

Engine Oil Cooler


  • Leaks in the core of oil cooler 

Cylinder Head Gasket


  • Leaks in the cylinder head gasket 
  • Damaged water seals 

Cylinder Head


  • Cracks in the cylinder head 

Cylinder Liner


  • Cracks in a cylinder liner 

Cylinder Block


  • Cracks in the cylinder block 

Recommended Actions

Leaks in the Cooling System

Pressurize the cooling system. Refer to Systems Operation/Testing and Adjusting, “Cooling System – Test”. If the test indicates a drop in pressure and no outside leaks are detected in the cooling system, there may be an internal leak. Make any repairs, as required.

Leaks in Core of Oil Cooler

Check for leaks in the oil cooler core.

Leaks in the Cylinder Head Gasket

Inspect the cylinder head gasket for leaks.

Damaged Water Seals

Inspect the water seal for damage.

Cracks in the Cylinder Head

Check for cracks in the cylinder head. If a crack is found, repair the cylinder head and/or replace the cylinder head.

Cracks in a Cylinder Liner

Check for cracked cylinder liners. Replace any cracked cylinder liners.

Cracks in the Cylinder Block

Inspect the cylinder block for cracks. If a crack is found, repair the cylinder block or replace the cylinder block.

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