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I too have repurposed a similar machine to try to help me solve a nagging problem. One of my vehicles uses a hydraulic clutch. By design, air bubbles can be tr

I too have repurposed a similar machine to try to help me solve a nagging problem. One of my vehicles uses a hydraulic clutch. By design, air bubbles can be trapped in the master cylinder due to factory bends in the lines and the orientation of the master cylinder when it is properly installed. If this happens it will be impossible to shift the gears (manual transmission) until the air is bled from the lines. I tried multiple air burping procedures without success. Part of the procedure involves tapping on the hydraulic lines to help dislodge air bubbles so they can flow up and out of the lines into the fluid reservoir. The area is tight and in order to do this efficiently you must remove the master cylinder from the vehicle. I decided to avoid that removal step and employ a Sharper Image back massager as a tool to dislodge air bubbles with the system in place in the vehicle. Since that massager is huge it would not fit into tight places under the hood so I used a length of PVC pipe held tight to the lines to transfer the vibration to the lines. This allowed me to get large air bubbles out of the lines. In the end I was not able to remove enough air using this hack because an O-ring near the bottom of the system is missing or bad and that allows air to enter and flow up so i could vibrate that thing all day and never get anywhere. It was a shot in the dark anyway. If that O-ring were not missing or bad I know it would work.

mh- 1y ago
I'm given to understand there are multiple companies manufacturing those back massagers in different shapes and colors these days, if you need one that can reach into those tight places under the hood without relying on the PVC pipe to help it along.
- doodlebugging 1y ago
  Sounds like a front massager. Different tools that certainly have their place, especially when there's no pipe handy.
  - goopypoop 1y ago
    yeah there's all sorts of useful shapes and convenient features, priced for every budget. Better in most ways! pipes just lead to trouble
    - doodlebugging 1y ago
      >pipes just lead to trouble I'm an old pipeliner. I can vouch for that.
    - MengerSponge 1y ago
      As I understand it you can even source them with specific bend and taper profiles, which lets you optimize for the geometry of the system you're trying to flush.
      - dotancohen 1y ago
        I've seen one recently that seemed to be long and skinny enough where if OP could see the part, he could vibrate the part. I have no idea what part of the human anatomy such a device is necessary for. Maybe top-of-the-foot while standing?
        epcoa 1y ago
        Near field Teledildonics
- mc3301 1y ago
  yeah, downhill mountain bike mechanics have used this method for brake bleeds for a while.
- amelius 1y ago
  You can buy vibration motors on AliExpress for $1.
userbinator 1y ago
For bleeding hydraulic brakes, which operate on a similar principle, the normal procedure is to open the bleeder valves on the slave cylinders and vigorously pump the pedal, refilling the master as necessary, until the fluid coming out of the bleeders is free of bubbles. Vibrating the lines won't do anything since the air bubbles fill their entire inside diameter.
- doodlebugging 1y ago
  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.
  - wutwutwat 1y ago
    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
QQQQQQQQQQQQQM 1y ago
Your issue with the o-ring reminds me of the time my buddy and I tried replacing the flex-line to one of his rear brake calipers. We rented one of the vacuum bleeder pumps from Auto-Zone, replaced the flex line, slightly loosened the bleeder cap and went to town. Sucked a ton of air out as the new line filled, but then there was a constant stream of tiny bubbles. He wanted to make absolutely sure that the line was clear, so he kept pumping and kept filling the reservoir. At first we thought maybe something about the way his original flex line failed catastrophically had introduced air all the way through the system, but the bubbles just kept coming. A full bottle of DOT3 later, we were questioning and trying to figure out where the bubbles were coming from, which turned into a fine-comb search of the entire brake line all the way back to the front of the car looking for pinholes, weeping, etc. After maybe 2 hours of searching, we found nothing. Continued pumping through a second bottle of DOT3, and then we realized that the air was seeping in through the threads of the bleeder cap and could be safely ignored. We felt real stupid. It's about time I do a brake flush on my car, so it's good I remembered this story so it's fresh in my mind.
- doodlebugging 1y ago
  I'm glad that something in the post helped you remember something useful. You are spot-on with your description of the situation. Good luck to you.
- stratosmacker 1y ago
  Something I've done to help with this is wrap the bleeder threads with PTFE tape. It will make a one time seal on the non-taper threads, but it's enough for a flush
wutwutwat 1y ago
pull a vacuum from the bleeder. problem solved. ps, if you haven't annihilated your syncros, you can 100% shift without the clutch, just "burp the throttle" when you want to shift, meaning, let off the gas, change gears, back on the gas. shifting up anyway. downshifting is another story, as is starting from a stop, though I've had good luck with a disabled neutral safety switch and stopping in neutral, turning the car off, pop into 1st, start when the light turns. Hell on the starter and battery, but sometimes it's the only option.
- doodlebugging 1y ago
  Thanks for this additional reply. Pulling a vacuum from the bleeder screw may be problematic since air can be pulled past the bleeder screws and you might not ever achieve a vacuum there unless you can install an open port in place of the bleeder screw and attach your MityVac or other tool to that port. I pulled vacuum at the reservoir end as was recommended in several forums and videos. It did pull air up to the reservoir but without straightening all the kinks in the system that act as traps it could not evacuate all the air. I spent multiple hours at 25 psi and never successfully bled the system. In theory it should work great though. I'm a longtime manual transmission driving speed-shifter with broad experience push-starting or roll-starting vehicles with dead batteries or other problems. I have even had one automatic transmission vehicle that could be started by putting the transmission into forward or reverse gear and turning the key so that the starter bendix drive pinion gear would engage and rotate the flywheel until it cranked the engine. Gasoline engine - 283 cubic inch Chevrolet with a PowerGlide transmission behind it. This was in a 1946 Chevy PU that had no top speed that I ever found. It would go faster until your own common sense took over. Downshifting and upshifting by RPM are useful skills for anyone driving a vehicle with a manual transmission. Catching the point where your RPMs allow you to slip into a lower gear takes a little practice. You should do like I did and refine your skills in an old Ford dump truck with dicey hydraulic brakes, one headlight bulb, no windshield wipers, and a 6 cubic yard load of crushed limestone in the dump bed. It's more fun that way.

mh- 1y ago

I'm given to understand there are multiple companies manufacturing those back massagers in different shapes and colors these days, if you need one that can reach into those tight places under the hood without relying on the PVC pipe to help it along.

doodlebugging 1y ago
Sounds like a front massager. Different tools that certainly have their place, especially when there's no pipe handy.
- goopypoop 1y ago
  yeah there's all sorts of useful shapes and convenient features, priced for every budget. Better in most ways! pipes just lead to trouble
  - doodlebugging 1y ago
    >pipes just lead to trouble I'm an old pipeliner. I can vouch for that.
  - MengerSponge 1y ago
    As I understand it you can even source them with specific bend and taper profiles, which lets you optimize for the geometry of the system you're trying to flush.
    - dotancohen 1y ago
      I've seen one recently that seemed to be long and skinny enough where if OP could see the part, he could vibrate the part. I have no idea what part of the human anatomy such a device is necessary for. Maybe top-of-the-foot while standing?
      - epcoa 1y ago
        Near field Teledildonics
mc3301 1y ago
yeah, downhill mountain bike mechanics have used this method for brake bleeds for a while.
amelius 1y ago
You can buy vibration motors on AliExpress for $1.

userbinator 1y ago

For bleeding hydraulic brakes, which operate on a similar principle, the normal procedure is to open the bleeder valves on the slave cylinders and vigorously pump the pedal, refilling the master as necessary, until the fluid coming out of the bleeders is free of bubbles. Vibrating the lines won't do anything since the air bubbles fill their entire inside diameter.

doodlebugging 1y ago
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.
- wutwutwat 1y ago
  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

QQQQQQQQQQQQQM 1y ago

Your issue with the o-ring reminds me of the time my buddy and I tried replacing the flex-line to one of his rear brake calipers. We rented one of the vacuum bleeder pumps from Auto-Zone, replaced the flex line, slightly loosened the bleeder cap and went to town. Sucked a ton of air out as the new line filled, but then there was a constant stream of tiny bubbles. He wanted to make absolutely sure that the line was clear, so he kept pumping and kept filling the reservoir. At first we thought maybe something about the way his original flex line failed catastrophically had introduced air all the way through the system, but the bubbles just kept coming. A full bottle of DOT3 later, we were questioning and trying to figure out where the bubbles were coming from, which turned into a fine-comb search of the entire brake line all the way back to the front of the car looking for pinholes, weeping, etc. After maybe 2 hours of searching, we found nothing. Continued pumping through a second bottle of DOT3, and then we realized that the air was seeping in through the threads of the bleeder cap and could be safely ignored. We felt real stupid. It's about time I do a brake flush on my car, so it's good I remembered this story so it's fresh in my mind.

doodlebugging 1y ago
I'm glad that something in the post helped you remember something useful. You are spot-on with your description of the situation. Good luck to you.
stratosmacker 1y ago
Something I've done to help with this is wrap the bleeder threads with PTFE tape. It will make a one time seal on the non-taper threads, but it's enough for a flush

wutwutwat 1y ago

pull a vacuum from the bleeder. problem solved. ps, if you haven't annihilated your syncros, you can 100% shift without the clutch, just "burp the throttle" when you want to shift, meaning, let off the gas, change gears, back on the gas. shifting up anyway. downshifting is another story, as is starting from a stop, though I've had good luck with a disabled neutral safety switch and stopping in neutral, turning the car off, pop into 1st, start when the light turns. Hell on the starter and battery, but sometimes it's the only option.

doodlebugging 1y ago
Thanks for this additional reply. Pulling a vacuum from the bleeder screw may be problematic since air can be pulled past the bleeder screws and you might not ever achieve a vacuum there unless you can install an open port in place of the bleeder screw and attach your MityVac or other tool to that port. I pulled vacuum at the reservoir end as was recommended in several forums and videos. It did pull air up to the reservoir but without straightening all the kinks in the system that act as traps it could not evacuate all the air. I spent multiple hours at 25 psi and never successfully bled the system. In theory it should work great though. I'm a longtime manual transmission driving speed-shifter with broad experience push-starting or roll-starting vehicles with dead batteries or other problems. I have even had one automatic transmission vehicle that could be started by putting the transmission into forward or reverse gear and turning the key so that the starter bendix drive pinion gear would engage and rotate the flywheel until it cranked the engine. Gasoline engine - 283 cubic inch Chevrolet with a PowerGlide transmission behind it. This was in a 1946 Chevy PU that had no top speed that I ever found. It would go faster until your own common sense took over. Downshifting and upshifting by RPM are useful skills for anyone driving a vehicle with a manual transmission. Catching the point where your RPMs allow you to slip into a lower gear takes a little practice. You should do like I did and refine your skills in an old Ford dump truck with dicey hydraulic brakes, one headlight bulb, no windshield wipers, and a 6 cubic yard load of crushed limestone in the dump bed. It's more fun that way.