Cummins N14 STC, Celect, Celect Plus – Service Manual Coolant Loss – Internal

Lubricating oil cooler is leaking

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

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.

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

Inspect the air compressor cylinder head and gasket. Refer to Procedure 012-003 in Section 12.

Aftercooler is leaking (aftercooled engines only)

Check the aftercooler and connections for leaks.

Rocker lever housing is cracked or porous

Inspect the rocker lever housing. Refer to Procedure 003-013 in Section 3.

Air or combustion gases are entering the cooling system

Check for air or combustion gases in the cooling system. Refer to Procedure 008-019 in Section 8.

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 head gasket is leaking

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

Cylinder liner is corroded or cracked

Check the cylinder liners for corrosion or cracks. Refer to Procedure 001-027 in Section 1.

Fuel heater is malfunctioning, if equipped

Check the fuel heater and replace, if necessary. Refer to the OEM service manual.