Probable Cause(s):
* Defect In Core Of Engine Oil Cooler
* Failure Of Cylinder Head Gasket
1. Defect in core of engine oil cooler:
Inspect cooler and make a replacement or repair defective oil cooler. Flush cooling system to remove oil.
2. Failure of cylinder head gasket:
Remove the radiator cap and with the engine running look for air bubbles in the coolant. Bubbles in the coolant are a sign of probable leakage at the head gasket. Remove the cylinder head from the engine. Check the cylinder head, cylinder walls and head gasket surface of the cylinder block for cracks. When installing the head, use a new head gasket. Tighten the bolts that hold the cylinder head according to the Specifications Section of the Service Manual.