Lubricating Oil System - Overview C Series Page F-12 Section F - Familiarization During operation the oil pressure will be higher than coolant pressure. A leak in the oil cooler will show as oil in the coolant. However, following an engine shutdown, the residual pressure in the cooling system can cause coolant to seep through the leak path into the oil. Aftercooler The aftercooler is also a source from which coolant can leak into the lubricating oil. Remove the aftercooler and look for evidence of leaking into the intake manifold. Pressure test the aftercooler element; refer to Procedure 010-008.
Cylinder Head Expansion Plugs The expansion plugs in the cylinder head under the valve cover is another potential for oil dilution. If possible, inspect for the leaks while the engine is warm. Remove the valve cover to look for signs of leaks. Pressurize the coolant system to 140 kPa [20 psi], if necessary. Cylinder Liner Seals Coolant can enter the lubricating oil through a deteriorated or damaged liner seal. Remove the oil pan and inspect the bottom side of liners with the cooling system pressurized.