New 2025 Mini S 2dr, noticed this hose between the battery housing and the coolant reservoir. Anyone know what the hose is for and if should be connected to something?

 

You're posting in the wrong place: this is the the R56 Mini forum (2007-2013). That said that looks like the drain line for the battery. Typically it would connect to an opening in the side of the battery to vent acid out of the car in the event of overflow or similar. There's usually a hole in each side of the battery: you insert the drain into one side and a plug (that should come with the battery) in the other, though many folks don't know this and miss it.

I haven't worked on a 2025 so that's just my educated guess, though.

 

Thanks Gubi, I hit the wrong post location, new to the forum. That being said, you are correct, it is the vent tube for the battery. I just looked at my 2024 clubman and noticed the same type of tube going to the battery. Just bought the new 2025 2dr s left over. The dealership most likely changed the battery after it sat for over a year and never fed the vent tube back to the battery. I just finished reattaching it. Thanks again just confirmed my suspicions.