My 2004 Jeep Grand Cherokee smells like the coolant is leaking. I have checked and can find no visible leaks nor puddles of coolant where I park. I topped off the coolant reservoir and was stunned to find it empty approximately 3 days later. My jeep is NOT overheating according to the gauges, the heater and AC both work. I am assuming I have a leak.. where and what could it be?

You probably have a crack or a bad gasket and the coolant is seeping into the combustion or lubrication systems. check for sweet coolant odor at exhaust pipe, maybe some green stain and drippings too. pull off the oil fill cap and pull out the dipstick, check for a foamy residue on either.

If you have no external leaks then it sounds like you could have a possible leak into the oil system(you would have a milky look to the oil) or the head gasket may have a small leak and the car is burning coolant but not big enough to overheat yet.you should have the system pressure tested as you could have an external leak small enough that the heat of the motor could be drying it before it accumulates enough to drip off the motor and yet smell.also the heater core could have a small leak in it and not show a leak.