While I was investigating an oil leak, which turned out to be an oil filter sealing ring issue, I noticed a "D" shaped opening at the bottom of the bell housing. Is this opening for ventilation or another reason, or has mine lost some kind of plug? This surprises me as I think it exposes the flywheel to all sorts of road splatter.

 

Perfectly normal. Don't worry

 

Thanks. Though I'm still curious about its purpose.

 

I did some work on my 09 clubman (manual) and it was closed! my countryman was open (auto). my other '11 clubman was open (manual).