Hi, I have a problem here. I was trying to drill through the firewall in my 97 expedition. I was drilling on the front passenger side where the floor starts to curve up and head into the dash. My drill poped through to metal and hit something else I guess. All of a sudden a green form started coming out. It sounded like air was escaping. What did I puncture? I have no idea and could really use some help. Thanks a lot!

 

Green? At first I though "coolant". But you also mentioned about air escaping. Could it be one on the lines to your AC core/condensor? Hope not. I guess you can check if your AC is working or not to rule this out.

 

Sounds like you punched a hole in the heater core.

 

You hit a heater line or the core somehow. If your truck was warmed up when you did this, that would be the sound of air escaping as the cooling system lost its pressure

 

Do not drive it. As mentionned you most likely popped the Heater Core. Actually you could drive it a short distance to a rad shop. It does have the fail-safe-cooling. If you want to change the core yourself you are looking at about 4-5 hours of work. The whole dash has to be removed. Once the dash is all unbolted you will need a second pair of hands to remove it from the truck. It is not difficult to do just tedious. The pain in my back has come back just reading about it.

JMC