I have a 2012 V6. Friday I had a very large puddle of coolant under my car. I checked the reservoir and it was about 1/2 full. My car never ran hot and no lights came on. I took it to the shop and they ran a pressure test and showed no leaks or problems. Any ideas as to what may have caused that to happen? There were no visible signs under the hood of where coolant may have leaked.