[Jager]

If you have coolant under the carpet in the trunk that could be the cap, or the tank, or the lines to/from the tank, remove the carpet panels to inspect around the tank. If there are no obvious signs there you will have to get under the vehicle and inspect.
What I have observed on water pump failures it seems to be related more to age of the vehicle... You are due. Is there any grinding noise from the front of the motor passenger side while the motor is running?