How do you get access to a coolant leak between the engine and firewall of a 1995 Oldsmobile acheiva?

You will definently have to jack up the car pretty high or put it on a lift. Make sure exactly where it is coming from, the heater lines or the heater core. The lines run into the core which can be a hassle to change. It sits under the dash and the inlet outlet shoot through the firewall to hook to the lines. Hope your one of the few lucky ones that has the leak on the outside and not in the floorboard.