On very rare occaisions I am noticing the smell of antifreeze when I start my car. It happens after I have driven it for a while, stopped somewhere for about 45 minutes and then gone out and started the car again. It only last for about 2 or 3 minutes. I have looked for leaks but do not see anything obvious. The last time I looked, I checked the coolant level and the the resevoir tank for about 3/4s empty. If the radiator cap is bad, would I see the leak right by the cap or could the leak be caused somewhere else?