[rrhyne]

Your brakes example is typical of someone who was never taught to work on their own vehicle.

Others have pointed out that it is not dangerous, so I’ll point out that it is emensely rewarding to do this kind of work yourself. Enlist a competent buddy and give it a try.

[SmellyGeekBoy]

Really? Years back I had the brakes completely fail on a classic Mini I'd worked on because one of the pipes wasn't fully tightened and all of the brake fluid pissed out the first time I applied the brakes. Thankfully I managed to grab the handbrake use that to stop (the Mini handbrake is cable powered and independent of the hydraulic system).

Do modern cars have anything to mitigate this?

[UncleEntity]

Pre-modern cars have something to mitigate this, testing your brakes more than a single pedal push before you go out on the road. Kind of sounds like you didn't even bother to bleed the lines which is also asking for a heap of trouble even if you managed to properly repair the entire braking system.

I've worked on the brakes on multiple cars and never once took one out for a test drive without triple-checking that I didn't make some stupid mistake that would put other people in danger.

Don't get me wrong, I had a couple cars with dodgy brakes over the years but always made sure they were good enough at the time I was driving them -- had this '53 Dodge that I had to bleed the brakes every time I wanted to take it out for a spin because the wheel cylinders were pitted and slowly leaked but always made sure to do a proper job because other people's lives were at risk too.

[chiph]

My understanding is that not all classic Minis had dual circuit hydraulic brakes. So if you have one of the originals with a single brake circuits, any leak means you will fail to stop (if fitted with drum brakes, stopping was doubtful anyway)