I have seen these appear to have headgasket failures but in realalty the real problem is that the timing chain guides wear out and the chain rubs a hole into the timing chain cover housing at the place where coolant passes thought it to the water pump. Symtoms are the oil turns into a chocolate milkshake and you may hear some timing chain rattling noise. To diagnose this requires removing valve cover, filling cooling system with water and do a pressure test. Inspect for coolant leaking into engine crakcase looking down into timing chain arear paying attention to the drivers side where chain rubs housing.
Fix is to replace timing chain and guides, install new timing cover housing. Change oil (recomend changing oil 2 times). Fill cooling system with tap water and a 1/2 bottle of dawn dish soap. Run engine without a thermostat to allow soap to clean system. Flush soap and water compleatly. Reinstall thermostat. Refill with fresh antifreeze and distilled water mix. Note: new radiator and heater hoses may be needed also depends on how long engine oil is in them and can attack the rubber from the inside.