Oil in Coolant
Oil Cooler Step 2 - To check for this condition wait until the engine has cooled off and remove the radiator cap to inspect, the oil will float on top of the coolant and is easily detected.
Oil in Engine Coolant
Transmission Oil Cooler Step 4 - When this cooler fails it allows transmission fluid to enter the coolant portion of the radiator causing transmission fluid levels to be low while creating overheating problems for the engine.
Transmission Fluid in Radiator Step 5 - Occasionally the head gasket can fail forcing oil pressure into the cooling jackets of the block or cylinder head. If all other testing has failed, the cylinder head must be removed for inspection of the gasket. Helpful Information These fluids may exchange places when these items fail due to pressures inside each system. Because engine and transmission oil pressure runs at about 40 psi and cooling system pressure runs about 18 psi oil is more likely to enter the coolant system rather than coolant entering the engine or transmission through the cooler.