Automotive hydraulic brakes

[paulmars]

regarding brake lines automotive. My understanding of hydraulics and how brakes work is that when you release the pedal it stops applying pressure to the brakes thru the hydraulic line, but it does NOT suck fluid back.

so as I see it closing the bleeder valve between each pedal push is not needed. If it did pull back in a tiny bit, that would be expelled during the next pedal push, right?

Also, most, although maybe not all, the bleeder valves ive seen point up or sideways, never down.

Just to be 100% over safe, I press fit a bleeder hose and let it travel up, before going over the suspension then facing down. So, there will always be fluid in this hose after the 1st pedal pump, so if it did pull a bit back (which I dont think it does) it would pull in fluid, not air. Then, I bleed each line like this and when I decide to stop, I just tighten the bleeder valve. No assistant needed.

Lately you do see a lot of videos where ppl have finally realized that you can bleed brakes with one person, but they have you put the end of the hose into a bottle filled with fluid. This makes no sense to me.

My understanding of ABS brakes, is that bleeding is the same method, just be extra careful not to let air into the system.

Ive read several different reasons why when you bleed, you start with the furthest away wheel. Is this really important?

Your thoughts to all my points?

Tks, p

 

[LittleInch]

Your first point only works if you release the pedal very slowly or you will suck air / old fluid back into the system.

They are on the top so that any air is expelled

The hose into the bottle is the same as your vertical hose. Despite your insistence that no fluid flows back, I'm afraid that often it does. Air is much worse to get into your hydraulic system than old fluid.

Starting with the furthest one clears all the fluid in the common legs first so you start with clean fluid when bleeding the ones closest to the pedal.

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[TugboatEng]

The pistons are designed to retract slightly when pressure is released. This draws air back in to the system. Also, the master cylinder side won't pump without some back pressure so you can't prime against an open bleeder.