Car is leaking coolant from between the engine and the firewall. The leak is about right in the middle of the car, between the driver and passenger sides of the car. Drips down on to the exhaust.

Started yesterday when we had a cold snap and I used the heater for the first time in months. How can I tell if it is the valve or the hoses? I am thinking hoses because from what I've read when the valve goes you either can't turn the heat off or you don't get heat. My heat works fine.

Assuming hoses, is this a big job?

I need the car next week for work. Short commute, maybe 5 miles each way. Is it safe to drive with less than a full gallon of water/antifreeze? I top up the reserve tank every time I drive but it will completely empty the radiator after about half an hour of driving around. Temp gauge climbs up to just under the red. I'll stop the car, throw in another gallon of 50/50 Prestone, and the gauge immediately drops to 1/4 (the 8 o'clock position if you will). Will briefly running it up to just under the red zone fry the headgasket? Or does that take prolonged overheating?