For 1990-2009 cars

Cause | Correction
--- | ---
DEFINITION: Foamy or discoloured oil or an engine oil overfill condition may indicate coolant entering the engine crankcase. Low coolant levels, an inoperative cooling fan, or a faulty thermostat may lead to an over-temperature condition which may cause engine component damage. Contaminated engine oil and oil filter should be changed.

1. Inspect the oil for above acceptable foaming or an overfill condition. Oil diluted by coolant may not correctly lubricate the crankshaft bearings and may lead to component damage. Refer to Lower Engine Noise, Regardless of Engine Speed .
2. Inspect by performing a cylinder leak-down test. During this test, above acceptable air bubbles within the cooling system may indicate a faulty gasket or damaged component. Refer to Cylinder Leakage Test .
3. Inspect by performing a cylinder compression test. 2 cylinders side-by-side on the engine block with low compression may indicate a failed cylinder head gasket. Refer to Engine Compression Test .

Failed cylinder head gasket | Replace the head gasket and components, as required. Refer to Cylinder Head Cleaning and Inspection and Cylinder Head Replacement - Left Side . Refer to Cylinder Head Replacement - Right Side .
Warped cylinder head. | Machine the cylinder head to the correct flatness, if applicable and replace the cylinder head gasket. Refer to Cylinder Head Cleaning and Inspection .
Cracked cylinder head. | Replace the cylinder head and gasket. Refer to Cylinder Head Replacement - Left Side or Cylinder Head Replacement - Right Side .
Cracked cylinder liner or engine block. | Replace the components, as required. Refer to Engine Block Disassemble in Engine Mechanical - 6.0L.
Cylinder head or engine block porosity. | Replace the components, as required. Refer to Engine Block Disassemble or Cylinder Head Replacement - Left Side or Cylinder Head Replacement - Right Side