I have flushed the entire coolant system, replaced thermostat, water valve assembly, turbo boost sensor, map, and mass air flow. WHY IS IT STILL OVER HEATING AND BUBBLING BACK UP IN THE RESERVOIR???? SOME ONE PLEASE HELP!!!!

 

Welcome from Florida, Symptoms are that of a blown head gasket.

 

oldchevy is most likely on the right track, but it’s important to determine when it’s over heating.

Is it happening all the time (driving or idle) or is it just when idling and slower speed driving?

If the latter, make sure the engine cooling fans are turning on.

If it’s the former, and/or it’s overheating even with the fans on, the head gasket is the likely cause. Pull the spark plugs to inspect for coolant in the cylinders.