For the TL,DR crowd, our method is below in bold if you want to skip the rest of the drivel.
Pumping the pedal on modern masters aerates the fluid. The more you pump, the more tiny bubbles you get in the fluid. That is bad and good. Bad because fluid shouldn't have tiny air bubbles in it, good because you can use that to tell when you have fluid from the master at each corner when you do a flush. When you see the tiny bubbles in the clear hose. Go to the next corner.
My method that we use is what works for
us, every single time. Others do it lots of different ways, I've tried most of them and I'm not able to make them work as well as a good 2 person manual bleed. They doesn't mean they don't work or aren't successful for others, I just can't make any of them work every time.
The problem with vacuum bleeders is sealing the straight threads of the bleeder screw at each wheel cylinder.
The problem with speed bleeders is you can't tell if you have a problem because you aren't able to see the flow and rate at each corner.
The problem with pressure bleeders is you can't always get enough pressure to induce the turbulence needed to get the crap out of the piston bores.
The problem with reverse pressure bleeding is you can push the crap that is in the piston bores up into the combo valve and master bore.
Here is ours again-
Cap off of the master and I flip it upside down and lay it back over the opening to slow down a splash that can happen. If the cap isn't off or loosened, a fast drop in reservoir level can produce a vacuum which makes the bleeding process harder. While the cap is vented, it is a very small vent designed to allow the pressure in the reservoir to equalize to atmospheric without leaking fluid. In case you ever wondered why some of the caps look the way they do.
View attachment 536283
Fluid level full in the master reservoir.
Engine off, key on to power up the dash, parking brake off. You need to know if the brake light is tripping which indicates a shifted shuttle valve.
The valve moves when the pressure is too high on one side. The low pressure side is being closed off or mostly closed off to prevent loss of fluid in the event of a leak. Good safety feature, terrible for brake bleeding. While we do use a lock out tool that replaces the switch in the combo valve to stop the shuttle from moving, we bled 100's of rigs before that and always managed to get it done easily. In fact, I kinda like not using one because that tells me the system is functioning, the valve will move when needed, and the circuit is good so it will work when it should. Roughly around 03-04, they changed something about the switch. Before then, we never had a single instance of the valve shifting during bleeding. After that, we get some rigs that had to have the dash light reset at every pedal push.
What put us onto looking for a better way or to bleed with the key on was I could hear the valve in the combo block clicking as it shifted.
I use a bottle to collect the fluid and a clear hose on the bleed screw. The hose end in the bottle does not have to be under fluid. That is an old wive's tale. If you want to verify why, simply open a bleeder and watch what happens. Fluid will run out which means air is not going in and again, we still have the issue of not being able to seal straight threads at the bleed screw so even if the requirement was to have the hose in fluid to stop air from going into the caliper, it would still get in around the threads, it doesn't. Even if it did, the bleeder is the high point, fluid would push the air up to the bleeder inside the caliper and it would leave at the next bleed cycle exactly as designed.
If you are not having the helper
push the pedal down enthusiastically enough that you have to hold the hose on the bleed screw, then they need to do so with some more enthusiasm. A pedal push down should squirt fluid out of the bleeder and across the floor 3-5 feet if you didn't have the hose in place.
1- you open bleed screw with as wide a swing as possible
2- helper pushes pedal to the floor and holds it at the bottom
3- close bleed screw and tell the helper to let the pedal up.
Repeat 5-7 times per corner.
I start with a gravity bleed. (remember the hose in fluid silliness?) When I have fluid dripping out of the bleeder at each corner, I know I can start the manual bleed. You can also use the gravity bleed to diagnose. If you open the bleeder on a full system and fluid doesn't come out after enough time that it should have, there is a problem.
The tiny bubbles in the fluid will coalesce after some time. A bleed the next day of 1-2 pumps per corner typically gets rid of them. If you do more pumps, you are putting more bubbles in the fluid. Granted, they will work their way back up into the reservoir or corner eventually but we don't need that if we don't have to.
If you have a problem that indicates there is air in the system, stop and find the problem. More bleeding isn't going to fix it. More bleeding just wastes time and fluid and will not ever solve a problem. Bleeding just gets air out of the system and if the above method doesn't do that, then the problem will not be fixed, found, or solved by doing more of it.
Last bit of annoyance I deal with frequently has to do with bench bleeding masters. If you could do it in the vehicle, it wouldn't be called bench bleeding.
I did not do much, practically no liquid was coming out when i changed the lines and calipers so I wasn’t thinking much of it