i have and it didn't harmed anything

 

Good enough for me! I'll trust your judgment hiwords.

 

yeah its ok. go to it.

 

Cool, thanks!

 

the next time you flush it, be sure to run water the opposite direction it usually goes. like in the bottom of the radiator. im not sure if you did that, but when i did a whole bunch of crap came out.

 

I actually did do that, but nothing unusual came out. I inspected and ran water through what seems like every individual part of my entire cooling system, but haven't seen any evidence of damage or corrosion. I even replaced my water pump and found nothing out of the ordinary. The only thing I found was that the exterior of my engine block was pretty rusty, but I'm guessing this is just typical surface corrosion and nothing to be too concerned about.

 

I ran that Prestone radiator cleaner through my cooling system for the recommended 6 hours worth of driving and saw quite a rusty discoloration in the water/cleaner mixture in the bottom of the expansion tank. Hopefully this is a sign of the cleaner doing it's job and not a sign of a problem beyond the capability of this product.