I follow all the recommended bleeding procedures for the assembly and since I did not want to remove the assembly from the vehicle to enable burping it, I improvised with the back massager, hoping to speed the process.

>you're putting pressure into a system filled with a fluid that does not compress, and air, which compresses a lot. The procedure for getting the air out of any system is pump the pedal, crack the bleeder, tighten, pump until you have pedal, repeat until no air comes out of the bleeder.

I agree that this is SOP for bleeding hydraulic systems. Been there, done that.

>you can get fancy with a vacuum too but one person on the pedal pumping and one person on the bleeder, you'll get all the air out.

In normal practice this also works. Many times though I am a one man band and I'm not bendy enough any more to be able to keep the pedal depressed with one leg while I contort and stretch over to the bleeder so I have resorted to using a section of PVC cut to length so that it can be jammed into the front of the seat base after rapidly pumping the pedal - holding the pedal at the floor, thus freeing the rest of my body to navigate to the bleeder.

>if you've been working on cars since the 70s, you'd know that what you're saying about "the usual pumping the clutch and cracking the bleeder valve process" being bad is nonsense. If you didn't bench bleed the master cylinder good enough, you're going to be bleeding things for awhile. Also, if you're dealing with abs, junction blocks, or bleeding wheels out of order you're going to be there awhile.

Like I said I have been turning wrenches since the late 1970's. Insinuating that I don't understand the process or problem well enough sounds powerful and righteous on your end but comes off as an unnecessary personal attack on my end. I've maintained foreign and domestically produced automobiles manufactured during the period from 1934-2022 including teaching myself troubleshooting of electronics and sensor-driven vehicles; heavy equipment on drilling rigs including mud pumps, air and hydraulic compressors, shakers, sniffers, MWD tools, LWD tools, downhole logging tools including electronics; backhoes, bulldozers, maintainers, dump trucks, water hauling trucks including air brake systems, jackhammers and compressors; small gasoline and diesel engines on yard tools and heliportable drilling rigs; rebuilt gasoline and diesel engines from a short block to an operating engine as a night mechanic for a seismic crew. I haven't done everything and I have no official certs but I have more diverse experience than most techs will get because I never walked away from an opportunity to tear something down to see how it worked. I'm pretty sure I understand the situation with this master cylinder system and like I mentioned, I followed the manufacturer recommended procedure for bench bleeding and when that didn't work I improvised. It didn't work because there was a bad o-ring in the master cylinder check valve that allowed air into the system whether it was on the bench or in the vehicle.

>clutch systems are a single line going from a mc to a hydraulic fork actuator. They take a whole 10 minutes to bleed starting from bone dry and you don't need to tap the air out, that what bleeding them is doing

I do not disagree with anything that you have said here but will leave this bench bleeding video [0] link for your own amusement. The fun starts at 4:31 in the video link. In my process, I substituted a back massager with a length of PVC pipe for the screwdriver since the master cylinder assembly was still installed in the vehicle. Prior to this, I bent or twisted the components so that it would be easier for air to flow up and out past anything that would normally be a trap.

[0] Perfection Clutch Bench Bleeding a Clutch Master Cylinder - https://youtu.be/91IYY_YENRw?t=271

A vibrator helped me debug a motorcycle brake light system