yup its the water pump, our pumps have a plastic impeller instead of metal one . so after about 50000 miles it can break and stop turning, if that happens it cant pump the coolant through the engine. i got rapped by my mechanic and spent 300+ on labor+ anew one, heres the funny part he replaced the broke one with a neither pump w/ a plastic impeller. If you felling up to it you can order a new one with a metal impeller from
http://www.spmotorsports.com/for 60 bucks and do it your self.