1/1/2’”hole in right lower front of airbox

[Forest Grump]

2014 F53 ACE. Change the air filter today and noticed that on the front lower right corner of the air box is a 1 1/2 inch hole into the airbox with a loose fitting plastic cap on it. Should this be remomoved and the hole left open. Is it a water fluid drain?

[javelin]

Looking down the list and no responses on your question......so.... my 2013 ACE 30.1 was delivered to me new with the engine air box round cap removed from that port. I think you are correct that it is a drain port since there were many issues with air boxes filling with water and soaking the air filters on some coaches, as I recall. You would think though that a drain port would be positioned facing down not facing the front cowl. I have been running with this port open since Sept 2012 and have never had a problem in heavy rains etc. Maybe it also acts as an air intake supplement to the normal snorkel inlet air which faces the passenger side in my coach.

[jb1911]

Any water drain would be on the bottom and would definitely be a lot smaller that 1 1/2" in diameter.

[javelin]

I had another look at the air box on my 2013 ACE 30.1 and the bottom of the air box is physically moulded lower to the left side and it also has a weep hole on the bottom side there (not at the lowest point though) that is not covered by the base plate which supports the air box....so that would likely mean there should be a cap on this 1-1/2 port. I also noted that the bottom of the port hole is not flush with the bottom of the air box which would be a likely requirement for easy water removal. So after 6 years of not having one I guess I should find a replacement or just tape over the opening. Maybe I have been lucky to never have had an issue to date. I also wonder if the MAF sensor on the engine side of the air filter would be affected with extra air coming into the air box, but I have also not had any engine issues since day one (knocking firmly on wood now).

[Bob Denman]

Even a "loose fitting" cap is there for a reason. I'd leave it in place, and ask the dealership about it...