a couple weeks ago I noticed my temp gauge moving up, pulled over to check the engine and saw my coolant running low... luckily I was right by my job and a friend brought me some coolant... everything seemed fine... a week later I decided to check the coolant and saw close to a quarter left... maxed it again checked 3 days later and close to half was gone... figured I may have a leak or something so i took it to the shop... they found no leaks, changed the radiator cap, lifted the car to remove any air bubbles etc, they found nothing wrong (this was on 07-15-09)... noted coolant at max... checked today and it was half gone... is this a normal thing? i know its hot in the valley... but this hasnt happened to me before... with any car... any suggestions on what to look for or what it may be?