Sounds like the overflow on the reservoir doing it's job. If not, I would check all the coolant hoses that run in front of the engine (between the engine and radiator), the ones on the drivers side above the transmission, thermostat housing, and heater lines. Since you can smell it, it's getting heated up. So, check the overflow, then concentrate on anywhere that there is coolant lines, and heat (engine block, headers, etc.). Good luck! Hope you find it!
Sean
