You didn't list the engine size so I can just offer some generalizations. If you don't see any puddles on the ground where you parked, a good suspect is a leaking cylinder head gasket. Your mechanic can perform a chemical test at the radiator to check for that. Another method is to add a small bottle of dark purple dye to the coolant, then check a day or two later with a black light. The dye will show up as a bright yellow stain that you can follow back to the source. If a head gasket is leaking, you'll find the dye inside the tail pipe.
Auto parts stores have the dye for the fluid you're checking, and those that rent or borrow tools should have a black light.
Sunday, September 6th, 2015 AT 8:00 PM