I have an 1982 El Camino 305 small block and am having troubles with determining if it is the gasket or the pump. I can't quite locate a leak, but it seems to centralize from the water pump and drip down the hose to the radiator. After my engine gets hot, which mind you my temp light has never turned on, and I shut of my car steam rolls out from behind my pump. I think it is the pump and please be it so. (Easier and cheaper fix. Replacement with a inexpensive part XP.)
There should be a weep hole on your water pump from where the antifreeze will be leaking if the seal is gone. Clean it up real good and try to see if that is where it is leaking from. Also check the thermostat gasket. If I remember correctly it is located above and just behind the water pump on a 305.
that would be a failing water pump, a head gasket would leak into the oil or exhaust most of the time.
Pull the oil dip stick if it has little bubbles on it and it is discolored you have a blown head gasket.Then pull your radiator cap when engine is cold, is it full or not? You can not trust what I call idiot lights because they usually come on after the damage is done.You can tell if the water pump is working by letting eng get to normal and grasp the top hose and squeeze it just a little,can you feel water running thru it,if not replace it.
Most likely it is the water pump... Probably leaking from the weep hole at the bottom of the pump and coolant is running down the lower hose. Head gaskets blowing on a small block Chevy is pretty rare unless you have ran it HOT!, which you have said you have not done. Use an inspection mirror and look under the pump just behind the pulley and see if the coolant is coming out of the weep hole. Small block Chevy water pump is inexpensive to buy.. Good luck
