Cummins N14 STC, Celect, Celect Plus – Service Manual Lubricating or Transmission Oil in the Coolant

Bulk coolant supply is contaminated

Check the bulk coolant supply. Drain the coolant and replace with non-contaminated coolant. Replace the coolant filters. Refer to Procedure 008-018 in Section 8.

Lubricating oil cooler transfer housing or lubricating oil cooler support is cracked or porous

Check the oil cooler transfer housing and the support. Refer to Procedure 007-047 and Procedure 007-003 in Section 7.

Lubricating oil cooler is leaking

Check the lubricating oil cooler for coolant leaks and cracks. Refer to Procedure 007-003 in Section 7.

Torque converter cooler or hydraulic oil cooler is malfunctioning

Remove and inspect the cooler cores and o-rings. Refer to the OEM service manual.

Cylinder head gasket is leaking

Check the cylinder head gasket. Refer to Procedure 002-004 in Section 2.

Cylinder head is cracked or porous

Remove the intake and the exhaust manifolds. Check for evidence of coolant leaks. If necessary, operate the engine at low idle. Pressure test the cylinder head. Refer to Procedure 002-004 in Section 2.

Cylinder block is cracked or porous

Inspect the cylinder block. Refer to Procedure 001-027 in Section 1.