I have a 99 doge neon that i just replaced the radiator in and i had the system flushed and everything was going fine til the next day. The car overheated when I drove around for a little over an hour. I opened the radiator cap and there is this white gunk everywhere it is not oil/water i know what that looks like.. is it possible they didn't flush it all the way and I just need to get the sealant out? I don't think it's the head gasket because there's no water leaking anywhere, no oil bubbling and it doesn't overheat quickly .. what would be the indication of possibly needing a new water pump? Oh, and already checked, fans are functioning properly and it has a new thermostat. Any ideas?