so in order for me to bleed the cooling system I need to loosen 2 of the bleeding valves that's on my car right?
?? Where do you get that there is more than 1 coolant bleeder. I ask because if you're getting info. from bogus sources, we need to let you know that.
There's only one bleeder. Follow the procedure in the FSM if you want to properly bleed it. No aftermarket manuals.
what are the impellers and how would I go about changing them
If you look at the rear (engine) side of a water pump, the disc that's 3 to 4" in diameter with spiral-shaped vanes is the impeller. So if the impeller is truly loose on the shaft of the water pump, you'd have to replace the whole pump. However, that's some expense and a bit of labor. Properly bleed the system before going to that trouble as that could very well be the problem.
Having said that, the timing belt change interval is 100k miles or 7 years, whichever comes first. Blow that off and you could end up with serious engine damage (when your timing belt breaks). So if the mileage or time on the belt is over that, replace it and the water pump ASAP. Use only OEM water pump as most aftermarket for this engine is crap (and frankly OEM water pump isn't that great either).
Also - *if* the water pump has been replaced, unless you know otherwise, there is in fact a good chance a crap aftermarket one was used, and maybe a loose impeller *is* the problem.
Sorry, but you've got some things to assess and decisions to make based on the above guidelines, but possibly with incomplete information.