I know the coolant is coming from behind the rear of the engine and the firewall but, due to the location, I can not see the exact source. I tried the mirror trick and still could not see it. However, I do see a trail of coolant coming from the top and then down the side of the union between the transmission and the engine on the passenger side. The coolant reservoir is half way full (or empty) but, I still do not see oil in it.
What else can it be? There is no other coolant source back there. Is there?
How long can I put this off if it is a blown head gasket? (without driving the car).