when you flush your engine, actually flush your engine, as in take one of the hoses off the heater and t in there, remove the lowest rad hose, open the heater from the controls in your car and run the hose, then put it back together but add a engine block flush cleaner and just leave it there overnight after running the engine for about 20min, then in the morning take it for a half hour drive. repeat the water flush process and ensure every little bit of the acid flush is gone, then top up the entire system using (looking at where you live) a 50/50 coolant to water mix, just by a expensive coolant, if it says made in USA then its going to be good.