In my 87 K5 Anti-Freeze is leaking inside of my cab right under the glove box. The truck started to leak when I turned on the heater. Then it would leak when I turned on my vents. Now its gotten to the point where it leaks all time and it gets worse the harder I press on the gas, plus my thruck is starting to over heat if I dont add water. I think its leaking from some part of the heater or has somthing to do with the heating systemin the truck. What can I do to fix this problem and what exactley might be the cause this leaking problem.