6.7L Cummins Troubleshooting – Coolant Loss – Internal

Radiator cap is not correct, is malfunctioning, or has low-pressure rating

Check the radiator pressure cap. Refer to Procedure 008-020 in Section 8.

EGR cooler leaking coolant

Check the EGR cooler for leaks. Refer to Procedure 011-019 in Section 11.

Air compressor cylinder head is cracked or porous, or has a leaking gasket

Inspect the air compressor cylinder head and gasket. Refer to Procedure 012-007 in Section 12.

Lubricating oil is contaminated with coolant

Check the lubricating oil for coolant. Refer to the Coolant in the Lubricating Oil symptom if the
lubricating oil is contaminated with coolant.

Internal coolant leaks

Refer to Procedure 008-020 in Section 8 to pressure test the cooling system and look for internal coolant leaks.

Variable Geometry Turbocharger leaking coolant

Refer to Procedure 008-020 in Section 8 to pressure test the cooling system and look for internal coolant leaks.

Cylinder head gasket is leaking

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

Cylinder head is cracked or porous

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 001-026 in Section 1.