Gonna try to install one of my 2x new SMC units...

The Dark Shadow said:
...........I cannot imagine that the problem will be resolved by one way check valves ...........
Click to expand...

You are absolutely correct on this one as well. They are just a convenience on your way to the perfect bleed job. Not a necessity.


The Dark Shadow said:
I'm doing things as their supposed to be done...
Click to expand...

Except now you are in troubleshooting mode. Hard to know exactly what is supposed to be done before indentifying the problem.
 
The Dark Shadow said:
There is zero pressure in the back brake, other than the spring. Zero hydraulic pressure. Zero.
Click to expand...

Could also happen because of air in the lines.

If you decide to do the quick bleeder 4 test, keep pumping the pedal although you feel no resistance and observe if the level in the MC reservoir is going down or not while you pump.

Route your clear tube on the cracked bleeder 4 straight to a container as you do that, so you do not have to worry about what is happening at this end while you pump the pedal and observe the fluid level in the rear MC reservoir.
 
Okay, so here's my best guess... The rear pedal doesn't seem to push any fluid into the system.

The rear master cylinder was working perfectly before I changed the SMC.

The SMC added air. I tried my brakes several times before removing all fluid then replacing.

Perhaps by using the brakes before I did "The Sequence", I introduced air into the rear master cylinder, rendering it ineffective, rendering all my operations ineffective...

What do you think...? This seems like a better explanation than foreign debris in the line.

If the master cylinder is indeed dry and not operational, how do I "prime" it...?

NOTE: The reservoir level does not change no matter how many times I operate the pedal (several hundred). This is why I'm guessing the master cylinder has been rendered ineffective.

What do you think?

MidLife said:
Could also happen because of air in the lines.

If you decide to do the quick bleeder 4 test, keep pumping the pedal although you feel no resistance and observe if the level in the MC reservoir is going down or not while you pump.

Route your clear tube on the cracked bleeder 4 straight to a container as you do that, so you do not have to worry about what is happening at this end while you pump the pedal and observe the fluid level in the rear MC reservoir.
Click to expand...
I tried just what you said. The reservoir does NOT go down. In fact, bit by bit, the reservoir raises.

It was 3/4 full to start, but now it is a couple mm from the top lip, so I stopped.

I ran into the reservoir overflowing several times (during day 1) during this process.

Seems counter-intuitive, to say the least.

Igofar said:
No, the service manual states something like "If you use a vacuum, follow their instructions". It does not tell you to Use a vacuum.
This system can be bled manually with just a hose, 8 mm wrench, and a catch bottle, by using the levers.
Click to expand...
Yes, I reread...

"Attach a commercially available air bleeder"

I took this to mean a vacuum, since that is what the local guy used who replaced my rear brake pads last year.

Vacuum, or no vacuum, the pedal does not seem to be pushing juice from the reservoir into the system. (See my response to MidLife above)
 
Push pedal down, close bleeder nipple, release pedal, push down pedal, open bleeder nipple, close bleeder nipple,release pedal, push down pedal, open bleeder nipple, close bleeder nipple, release pedal, repeate until you get brake fluid wether you use a one way valve or not. Some times one way valves don't work without fluid in them.
 
David Fyffe said:
Push pedal down, close bleeder nipple, release pedal, push down pedal, open bleeder nipple, close bleeder nipple,release pedal, push down pedal, open bleeder nipple, close bleeder nipple, release pedal, repeate until you get brake fluid wether you use a one way valve or not. Some times one way valves don't work without fluid in them.
Click to expand...
Did it nearly 200 times... Literally. No joke! The fluid is refilling the reservoir rather than being sucked from the reservoir (when I don't have a vacuum attached).
 
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The Dark Shadow said:
Okay, so here's my best guess... The rear pedal doesn't seem to push any fluid into the system.

The rear master cylinder was working perfectly before I changed the SMC.

The SMC added air. I tried my brakes several times before removing all fluid then replacing.

Perhaps by using the brakes before I did "The Sequence", I introduced air into the rear master cylinder, rendering it ineffective, rendering all my operations ineffective...

What do you think...? This seems like a better explanation than foreign debris in the line.

If the master cylinder is indeed dry and not operational, how do I "prime" it...?

NOTE: The reservoir level does not change no matter how many times I operate the pedal (several hundred). This is why I'm guessing the master cylinder has been rendered ineffective.

What do you think?


I tried just what you said. The reservoir does NOT go down. In fact, bit by bit, the reservoir raises.

It was 3/4 full to start, but now it is a couple mm from the top lip, so I stopped.

I ran into the reservoir overflowing several times (during day 1) during this process.

Seems counter-intuitive, to say the least.


Yes, I reread...

"Attach a commercially available air bleeder"

I took this to mean a vacuum, since that is what the local guy used who replaced my rear brake pads last year.

Vacuum, or no vacuum, the pedal does not seem to be pushing juice from the reservoir into the system. (See my response to MidLife above)
Click to expand...
Page 17-8
WHEN USING A COMMERCIALLY AVAILABLE AIR BRAKE BLEEDER, FOLLOW THE MANUFACTURER'S OPERATING INSTRUCTIONS.
 
Page 17-7 TROUBLESHOOTING
READ: Brake lever/pedal soft or spongy causes
Air in hydraulic system
Leaking hydraulic system
Worn caliper piston seal
Worn master cylinder piston cups
Worn brake pad/disc
Contaminated caliper
Caliper not sliding properly
Low brake fluid level
Clogged fluid passage
Sticking/worn caliper piston
Sticking/worn master cylinder piston
Bent brake lever/pedal

As you can see there are several things that can cause the issues you are having.
Focusing on just one, and not considering/checking all the other possible things will work against you.
If you think something is clogged, remove the bleeder in question, pump the lever and see if fluid or air exits.
You can check every bleeder you've touched if you feel you need to.
Attempting to ride the bike, after you replaced the SMC, before you did a complete/correct bleed probably moved a lot of air, in a lot of hard to reach places, and its probably just going to take time and patience to get it all back out.
 
You might double check your bleeder is not clogged and just remove it. At least until you start getting brake fluid spilling out. I had a car once that had a corroded bleeder that didn't work, took me a while to figure out I was just "pulling air" from around the bleeder head and not through the brake lines.

I think it is in the article related to bleeding, but you are aware there are two separate bleeding screws on the rear caliper?
1715898186925.png

Good luck! We are all anxiously watching and hoping for that "ah-ha!" moment. :)
Ryan
 
Thanks Ryan, good point, but that has been suggested several times, just don't know if its been done or not yet.
I've found the rearmost bleeder often clogged with rust and crap, and suggested that this be removed to see if fluid comes out without the nipple in place.
Keeping fingers crossed.
 
Thanks Larry and Ryan for your thoughts...

I've had fluid come through every bleeder. Had 3 completely out and they were fine showing zero degradation.

One fellow on a Facebook group said he had to pump the brake pedal frantically (about 30 or more times about once per second) before any pressure would push through...
 
The Dark Shadow said:
Perhaps by using the brakes before I did "The Sequence", I introduced air into the rear master cylinder, rendering it ineffective, rendering all my operations ineffective...

What do you think...? This seems like a better explanation than foreign debris in the line.
Click to expand...

Good thinking, worth looking into. You need the get the rear MC to "pump". There is no bleeding or braking without it.

One way to "prime" it would be to undo the banjo bolt on top of the MC and start pedal pumping until you have fluid coming out of it. You can also completely remove the bolt and when you see fluid starting to come out, feel that it is solidly building up pressure by putting your finger on it.

Also make sure the MC piston is actually moving, is not stuck.

Have not done that myself on the ST. Looks like you may have to remove the foot rest support to get to it. Experts will tell you.

Use plenty of rags to collect fluid and protect paint while doing that and soapy water on hand for cleanup.

One trick you may want to try first that may be easier and might work, is "reverse bleeding", where you force fluid back to the reservoir through the MC by pumping fluid into the bleeder (try #4).

You can use a syringe like this one to stick into the clear tube for feeding the bleeder. Make sure to get the air out of tube and syringe before connecting to the bleeder, and scoop out fluid out of the rear reservoir you will be feeding into.

 
Perhaps you can reach out to the person on Facebook and ask them for assistance, and how they solved their problem.
Maybe they can help you.
 
Okay, so how do I access and remove the rear MC...?

It's not doing a thing (not pumping any fluid)...

Are there parts inside it that can come loose or break...? My back brakes were fine until I changed the SMC.

There is nothing "easy" about this.

So far, I've spent over 20 hours, a hundred bucks and more of tools, and all I've succeeded in doing is screwing up my bike worse and becoming more stressed and despondent.

And if I need to take off the metal side panel (to access the rear master cylinder) I need to buy more tools since I don't have allen keys large enough...

And I lost a bleeder nozzle attachment inside the black hole of the bike... lol (update... I got the nozzle back.)
 
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Hey Shadow, if this makes you dizzy just sit back and let the collective brain sort out and simplify if there is anything relevant here from my thoughts.

Reservoir gains fluid when pumping after disconnecting vacuum bleeder following pumping with assistance from vacuum bleeder.

How can this be?

For pressure to enter the reservoir, there must be a pressure a pressure differential.
Two possibilities to consider.
There must be lower above the reservoir fluid level than below.

The vacuum pump created a low pressure under the reservoir.

How can the level rise after removing the vacuum bleeder and closing the bleed nipple after crea overall lower pressure under the reservoir?

Run this hypothetical scenario.

We apply vacuum under the reservoir.
This shrinks the volume of air in the system under reservoir, therefore pulling the fluid towards the vacuum and lowering the fluid level.

The nipple is then closed.

Pressure should be equal above and below the reservoir because there is a port in the mc that is exposed when the lever is relaxed.

If we see the level rise some time after disconnecting the vacuum and closing the bleeder, there must be a period of time when there is still a vacuum in the system after closing the nipple.

There is a small leak that allows outside into into a space under vacuum to grow in volume to push the fluid level up. Or at some component between the applied vacuum and the fluid surface level, there is a blockage so small that it allows the vacuum bleeder to pull a vacuum then slowly releases it either because of or coincidentally or both, when the brake lever is exercised after the vacuum procedure.

Sorry I got to go eat breakfast with sweetheart without proof reading.
 
SMSW said:
With all due respects to Larry, I used a vacuum pump on my bikes (Guzzi, ST1300, VStrom) with no problems at all.
Click to expand...
I'm going to jump in here for a second and point out that a vast majority of problems with vacuum bleeders is the hose seal. The avg consumer uses the stock hose that comes with the bleeder and that only encourages bad seals on the calipers.
 
aniwack said:
I'm going to jump in here for a second and point out that a vast majority of problems with vacuum bleeders is the hose seal. The avg consumer uses the stock hose that comes with the bleeder and that only encourages bad seals on the calipers.
Click to expand...
This has been my experience. We've all seen the MityVac and it's lookalikes, but even when buying aquarium hose and the like which fit better, this has always been a very messy endeavor. The MotionPro bleeder recommended by Larry and others here work much better for me.
While the MityVac seems to be a good solution, in theory, maybe it's just me. But it's a train wreck and a kludge when I have tried to use it on my motorbikes, and all the accessory nipples are useless. Perhaps the metal ones are better, I dunno, I have the plastic one like this one.

MityVac.jpg
 
sirbike said:
Hey Shadow, if this makes you dizzy just sit back and let the collective brain sort out and simplify if there is anything relevant here from my thoughts.

Reservoir gains fluid when pumping after disconnecting vacuum bleeder following pumping with assistance from vacuum bleeder.

How can this be?

For pressure to enter the reservoir, there must be a pressure a pressure differential.
Two possibilities to consider.
There must be lower above the reservoir fluid level than below.

The vacuum pump created a low pressure under the reservoir.

How can the level rise after removing the vacuum bleeder and closing the bleed nipple after crea overall lower pressure under the reservoir?

Run this hypothetical scenario.

We apply vacuum under the reservoir.
This shrinks the volume of air in the system under reservoir, therefore pulling the fluid towards the vacuum and lowering the fluid level.

The nipple is then closed.

Pressure should be equal above and below the reservoir because there is a port in the mc that is exposed when the lever is relaxed.

If we see the level rise some time after disconnecting the vacuum and closing the bleeder, there must be a period of time when there is still a vacuum in the system after closing the nipple.

There is a small leak that allows outside into into a space under vacuum to grow in volume to push the fluid level up. Or at some component between the applied vacuum and the fluid surface level, there is a blockage so small that it allows the vacuum bleeder to pull a vacuum then slowly releases it either because of or coincidentally or both, when the brake lever is exercised after the vacuum procedure.

Sorry I got to go eat breakfast with sweetheart without proof reading.
Click to expand...

So to finish that post I want to say that it could support shadow’s theory that there is a blockage, though more specifically a partial blockage.
And that it is likely to be at the master cylinder while not completely eliminating possibility of a problem in another component.

Regarding the use of a vacuum bleeder. I think in this instance it may be providing diagnostic information. And I don’t think that DS has successfully progressed through the bleeding procedure far enough for the failings of the vacuum bleeder for it to have caused an issue. In other words this theoretical blockage is a bigger problem.

Generally I have found that using mine helps me get fluid in but it is not a good tool to complete the bleeding procedure due to the problems pointed out in this thread.
 
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aniwack said:
I'm going to jump in here for a second and point out that a vast majority of problems with vacuum bleeders is the hose seal. The avg consumer uses the stock hose that comes with the bleeder and that only encourages bad seals on the calipers.
Click to expand...
I have been able to confirm that the attachments I'm using are creating a full and effective seal. It is certainly good to eliminate this possibility, but this is not the issue.

I won't argue that the vacuum system I used could have caused my issues. I don't know anything about this procedure that is certainly anything but easy for me. I don't know $h1t about it otherwise I wouldn't be having these problems.

For some people, things that are unstated and easy do's and don'ts for me are clueless, and I could have destroyed my system out of pure ignorance.

But the fittings I'm using are sealing properly.
 
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