It’s 10 years old, I don’t think it’s sealing as tight as when new.

 

Replacing the rubber is not enough?

Here's the thing, the reservoir is plastic. Metal might cause it (the res) to wear¿?

 

True. Although using it once every other year shouldn’t be an issue. I’m using it every other year on 2 cars though, and I’ve done several bleeds for friends and family. It just didn’t seem to seal as tight last time I used it.

Maybe I should just get a new plastic one

 

I'd start with just replacing the oring.. Recall there's 2 different sizes that it comes with. The thinner one is the one to use iirc.