does anyone can tell me what is that for?

[Benny17441]

And while you are at it, take a good look at the hoses, they may (probably) need replacing too. Instead of using cheap hardware store slotted hose clamps, use solid all SS hose clamps, like Scandvik ABA clamps.

Well you got the message, we are a little subtler down here when telling other people what to do.