2018 xc300 - front brake disappearing and needs constant pumping

[(F5)]

An 18 seems so new. But if it has a bunch of hours maybe that's 5 years of wear.

I've come across master cylinders that don't improve with rebuild. The issue is an alloy bore and a sinusoidal lever push. The bore wears like an hourglass.

I bought a new mc for mine and all of a sudden after every other thing it came right.

I'd tried Chinese ones but weren't right. A new one out of Italy of all places was surprisingly cheap on evilBay.