2008 Saturn Sky Redline Ecotec Turbo 2.0t with 100k miles - After scratching my head for weeks and replacing the water pump and thermostat twice, power flushing the radiator, the block, and heater core twice, the Sky would still overheat and I was pulling my hair out. Finally found the issue. Broken guide led to slack in the chain which led to all teeth being ground off the crank sprocket.
While there, checked the oil pump for lose debris and shavings. All new timing comments, new guides, new chains, new tensioners, new belts, new seals, and much much more! ALL GOOD and BACK TO IT for another 100k miles!
This should have been the very first thing I checked but now I know for next time.
I HOPE this helps someone else!
