C Series Lubricating Oil System - Overview Section F - Familiarization Page F-11 Oil Dilution Diluted oil can cause severe engine damage. Inspect the condition of the oil. Thin, black oil indicates fuel in the oil. Milky discoloration is an indication of coolant in the oil. Coolant-Diluted Oil Coolant in the oil results from a crack or leak between the coolant and oil circuits. The possibility for intermixing can occur in these components: Oil cooler Aftercooler Core plugs in cylinder head Cylinder liner seals Head gasket Cylinder liner (crack) Cylinder head (cracked passage) Cylinder block (cracked passage) Air compressor (coolant cooled).
Oil Cooler The oil cooler design does not require gaskets or seals to maintain the separation of oil and coolant. If either the coolant or oil is contaminated, check for a leaking oil cooler element; refer to Procedure 007-007.