I've been wrenching since my teens in the late 1970's and have learned a lot over that long time span. I was following, sometimes to the letter other times to the spirit, the documented procedure for burping this particular hydraulic clutch system. The system has bends from the factory that act to trap air and most aftermarket parts arrive pre-bled so that the installer doesn't need to deal with the issue because it is such a PITA to bench bleed these systems.
Bench bleeding involves straightening the lines and orienting the components along the lines, the master cylinder especially, so that air bubbles can flow up thru the lines by gravity and then using a tool to tap the lines and dislodge any bubbles so that they flow up to the fluid reservoir. I decided to hack the process using that back massager to speed up the gravity flow of any trapped air instead of using a screwdriver to tap the lines as they do in the official maintenance procedures. I also left all the parts in the vehicle making access to some curves or bends very difficult. That is why I used the PVC. It allowed me to transfer the vibration to the lines all along the length without removing anything from the vehicle.
I had already tried the usual pumping the clutch and cracking the bleeder valve process and though disappointed, was not surprised to have no success since it usually only works when the air is trapped low in this system inside the clutch slave cylinder near the bleeder valve, not higher up in the section containing the clutch master cylinder.
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.
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.
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.
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 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.
Bench bleeding involves straightening the lines and orienting the components along the lines, the master cylinder especially, so that air bubbles can flow up thru the lines by gravity and then using a tool to tap the lines and dislodge any bubbles so that they flow up to the fluid reservoir. I decided to hack the process using that back massager to speed up the gravity flow of any trapped air instead of using a screwdriver to tap the lines as they do in the official maintenance procedures. I also left all the parts in the vehicle making access to some curves or bends very difficult. That is why I used the PVC. It allowed me to transfer the vibration to the lines all along the length without removing anything from the vehicle.
I had already tried the usual pumping the clutch and cracking the bleeder valve process and though disappointed, was not surprised to have no success since it usually only works when the air is trapped low in this system inside the clutch slave cylinder near the bleeder valve, not higher up in the section containing the clutch master cylinder.