leaking brake valve

^^ I would do that. Most of the new copper sealing washers sold these days with all sorts of brake parts are a lot harder than the ones that used to be sold, and the new ones can be ridiculously hard to seal. I have not cut one apart but I suspect they are a copper coated steel or just a copper colored alloy. Where to get the older style, softer copper sealing washers is a good questions.

Or even brass nowadays, and it causes the same problems.
I noticed some of the replacement oil drain plug washers are brass now also.

Anything to cut costs I guess.