As far as I can see from the photo that you sent, this hole is usually closed, only tightly! And nothing is attached there. I don't quite understand that they wanted to join him, or maybe they just put it on and forgot to close it. This often happens with machines that buy used, sometimes such caps are seen that the hair rises. Cool thing for this vehicle inspection report but it is not everywhere, few people use it, but it is very useful. I still see your other hoses in poor condition, so I would advise you to take care of them while there is time.