christmas morning i started my car up for it to warm up b4 i went on my drive....i do this every morning b4 work and normally when i get in, tha car is warm and toasty, but it wasn't this time, the heater just blew out cold air, i pulled the car back a lil and i had a slight coolant leak, but it wasn't from the radiator.....i drove the car and the air was still cold and then when i made a left turn, it got really warm and then cool again.....then it seems only when i hit 4th gear, it will get hot, but at idle, its cool air!!! at the present moment i am flushin the radiator and coolant system.....any ideas at what might be the problem fellas.....could this be a sign of my water pump about to go out???? need help quick....its not fun ridin in a cold car when its 29 degrees at night!!!