I replaced my 12v optima battery, and noticed this little black hose that comes up through the floor in the back. I didn’t notice disconnecting it, and don’t see where it went. Can anyone tell me what this is, maybe just a vent? Also found there was an inch of water in the bottom of the well.
It is the vent for your 12 volt battery. Your optima had a vent don’t know what you bought. Try to address that rust if not it will eventually rot out and the bottom will fall out there’s a lot of weight on that area. Few posters that had happened to quite a hassle to fix it. It’s probably rotted under you spare tire too. the water drips right on the hybrid battery fan connector too and rots it out. That will throw a red triangle of death. good times
