Water is leaking from my a/c on the driver's side. I have a 2004 GS Eclipse and was told this is a fairly common issue from 2000-2005. A mechanic just blew out the line and thought it would be fine, it wasn't. My car flooded again. I called Mitsubishi and they said it is a $16 (#MN121314) part but with 5 hours labor it would be $616!! It goes between the evaporator case and the firewall and to get to it you have to remove the dash. Another mechanic suggested an "O-ring" or even a small hose on the nipple between the firewall and evaporator, would either of these other methods work? Any help would be greatly appreciated!!

 

If it is drivers side only (not passengers side) it could be the gasket around the AC drainage hole going through the firewall is worn out and rotted. Due to the design, liquid exiting while running your AC can seep through the bad gasket and back into the drivers side floorboard.

Pulling the carpet back from under the gas petal and you can see the faint discolored path the water takes down into your drivers side floor.

If this is the case, the fix is simple. Locate the leak from the engine bay by shining a flashlight down against the firewall behind the engine... you will know where it is due to the discoloration and see the small rubber drainage hole and gasket surrounding it. It's tiny and way down in there and you will wonder how the heck you can reach that! Remove your battery and battery tray (really easy) and buy some water proof epoxy sealant ($6 or so). Use a rubber glove because you're gonna have to do it by feel (just enough room to stick an arm in there) put a dab of epoxy on your fingertip and put the epoxy around the outside of the drain hole to prevent water from seeping through the bad gasket. Do NOT block the hole water is supposed to come out of.

Fixed the problem for me!