I know this is an old thread but I couldn't find much info on the topic. I was experiencing a small coolant leak occasionally. About 1/4 oz at most. I hunted all day for where it could be coming from. Turns out that it's coming from the block heater. I didn't even know it had one!!! Sure enough I found the plugin tucked into some wiring on top of the radiator fan.
The location of the block heater is on the back of the block (near the firewall) directly above the oil pan drain plug. It's way up there and you can barely see it from underneath. I've attached 2 pictures showing it's location.
