Most likely the waterpump.
You would not be able to reach 7000rpm without a custom chip, which I assume you do not have. 6750 is as high as you would get at that wouldn't do any damage.
Waterpumps are COMMON failures. replace it with a white plastic one, or a metal one, but DO NOT USE a black plastic one. Cost about $60-$70 and 25 minutes to do it yourself. DO NOT PAY A MECHANIC to do this!
Use the search link (at the top of every page) to search for waterpump removal, just make sure to change the box that says "date range" to "all".. search in troubleshooting, or duratec maintenance.)
Ray