C13, C15, and C18 Engines Troubleshooting – Coolant Contains Oil

Probable Causes

  • Engine Oil Cooler
  • Power Train Oil Cooler (if equipped)
  • Water-Cooled Turbocharger
  • Cylinder Head Gasket
  • Block

The procedures have been listed in order of probability. Complete the procedures in order.

Verify the presence of oil in the coolant with a scheduled oil sample. Verification must be made before performing the procedure.

Recommended Actions

Table 1
Troubleshooting Test Steps Values Results
1. Leak in the Engine Oil Cooler

A. Check for leaks in the engine oil cooler. Refer to Testing and Adjusting for the proper procedure.

Oil Cooler Result: A leak is found in the engine oil cooler.

Install a new oil cooler core. Refer to the Disassembly and Assembly manual.

Flush the cooling system. Refer to the Operation and Maintenance Manual for the proper flushing procedure. Refill the cooling system with the proper coolant. Refer to the Operation and Maintenance Manual for the correct coolant and capacities.

Check the oil for coolant. If coolant is found in the oil, drain the crankcase. Refill the crankcase with the proper oil after the leak has been repaired. Refer to the Operation and Maintenance Manual for the correct oil capacities and viscosity.

Result: A leak was not found in the engine oil cooler.

Proceed to Test Step 2.

2. Leak in the Power Train Oil Cooler

A. Check for leaks in the power train oil cooler. Refer to Testing and Adjusting for the proper procedure

Power train cooler Result: A leak is found in the power train oil cooler.

Install a new oil cooler core. Refer to the Disassembly and Assembly manual.

Flush the cooling system. Refer to the Operation and Maintenance Manual for the proper flushing procedure. Refill the cooling system with the proper coolant. Refer to the Operation and Maintenance Manual for the correct coolant and capacities.

Check the oil for coolant. If coolant is found in the oil, drain the crankcase. Refill the oil after the leak has been repaired. Refer to the Operation and Maintenance Manual for the correct oil capacities and viscosity.

Result: A leak was not found in the power train oil cooler.

Proceed to Test Step 3.

3. Water-Cooled Turbocharger (if equipped)

A. Inspect the turbocharger for cracks.

B. Remove the oil drain line from the turbo and pressurize the cooling system, Refer to Testing and Adjusting, “Cooling System – Test”.

C. Check the turbocharger for coolant leakage.

Turbocharger Result: The turbocharger is cracked.

Replace the turbocharger. Refer to the engine Disassembly and Assembly for the correct procedure.

Flush the cooling system, Refer to the Operation and Maintenance Manual for the correct procedure.

Refill the cooling system with the proper coolant. Refer to the Operation and Maintenance Manual for the correct coolant and capacities.

Check the oil for coolant. If coolant is found in the oil, drain the oil. Refill the oil after the leak has been repaired. Refer to the Operation and Maintenance Manual for the correct oil capacities.

Result: The turbocharger is not cracked.

Proceed to Test Step 4.

4. Cylinder Head Gasket

A. Remove the cylinder head. Refer to the Disassembly and Assembly manual.

B. Check the cylinder liner projection. Refer to the Systems Operation/Testing and Adjusting manual.

C. Install a new cylinder head gasket and new water seals in the spacer plate. Refer to the Disassembly and Assembly manual.

Cylinder head gasket Result: New cylinder head gasket and water seals were installed.

Proceed to Test Step 5.

5. Cylinder Head

A. Check for cracks in the cylinder head. Perform a leak test on the cylinder head. Refer to System Operation, Testing and Adjusting for the proper procedure for checking the cylinder head.

Cylinder head Result: A crack is found in the cylinder head.

Repair the cylinder head and/or replace the cylinder head. Refer to the Disassembly and Assembly manual.

Result: A crack is not found in the cylinder head.

Proceed to Test Step 6.

6. Cylinder Block

A. Inspect the cylinder block for cracks.

Cylinder block Result: A crack is found in the cylinder block.

Repair the cylinder block or replace the cylinder block. Inspect the top deck. Refer to the Reuse and Salvage Guidelines for the proper inspection procedure.

Complete the procedure in the order in which the steps are listed.

If the procedure did not correct the issue, contact your Cat dealer Technical Communicator (TC). For further assistance, your TC can confer with the Dealer Solutions Network (DSN).

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