Well my car was running hot and leaking coolant so I took it to the dealer to find out where it was leaking. They told me it was the water pump so I replaced the water pump tonight. Now the car is running hot and leaking coolant. I'm pretty sure I did everything in the install right. I tightened down the radiator drain screw. Could it not be on there tight enough? I don't think its a coincidence that it has the exact same symptoms as before. The heater is intermittent cold/hot so I guess this means there is air going through the heater core at some point. However, while the low coolant light is on and it runs hotter than normal, it never gets above 210 (usually, if it does I pull over). Please help me with what else it could be, thanks

Forgot to mention, the coolant appears to be leaking more towards the passenger's side and when I have it off with the hood popped after the engine's been running, there is a sort of hissing noise near the radiator cap, and an occasional gurgle sort of like a toilet flushing back near the heater core.

 

You need to pull the throttle body coolant line off and refill the radiator 'till coolant comes out of the heads. Driving around without it properly bled and full can cause serious damage to the motor.
Then try to find your leak.

 

now just to let you know it could bet the thermostat or you might need a new radiator cap too... but you running on low coolent could cause the pump to go out. so the pump might have been only part of the problem...