Since the lubricating oil cooler design does not require gaskets or seals to maintain the separation of oil and
coolant, the element itself must leak to allow mixing of the fluids (refer to page 2-18 for the replacement and oil
cooler testing procedures).
During operation, the lubricating oil pressure will be higher than coolant pressure. A leak in the lubricating oil cooler
will show as lubricating oil in the coolant.
However, following an engine shutdown, the residual pressure in the coolant system can cause coolant to seep
through the leak path into the lubricating oil.
To check for leaks, pressurize the cooling system to 140 kPa [20 psi]. With the system pressurized remove the
following components and inspect for leaks.
• Valve covers (leaks indicate cracked head)
• Lubricating oil drain plug (leaks indicate defective lubricating oil cooler, head gasket, cracked head or block)
• Tappet cover (expansion plug leak)
Coolant in the lubricating oil can be caused by a damaged cylinder head gasket or cracked cylinder head or block.
Remove the cylinder head and gasket and inspect for cracks or damage.
