On 2 previous occasions my s3 spider dumped a puddle of antifreeze on the garage floor after being parked. It seems to be coming from the front passenger side of the engine. I think it has only happened when the heat valve was open...I think! It's baffling because I see almost no evidence of coolant on anything, except a few old stains on the bottom of the ac compressor and some slight wetness around the water pump. It happened again last night. Today I ran it up to temp after topping up and bleeding the system. I drove it up on ramps and crawled underneath while it was running. Not a drop. I put a sheet of cardboard under it, so I could get a better handle on the origin, and let it cool. Still nothing!