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Pruneman99
Samba Member
Joined: February 22, 2012
Posts: 5013
Location: Oceanside
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 Posted: Sun Mar 19, 2023 7:07 am Post subject: Re: Brand new master cylinder; still no pedal. |
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| viiking wrote: |
The only problem I have about “stabbing” the pedal is that overly violent “stabbing” can break big air bubbles into micro bubbles. These micro bubbles can take time to re-coalesce and can extend the time taken to bleed the brakes.
IMO bleeding should always be done SLOWLY. Slow on the way down and then back up.
Once the air has gone, then stabbing will no longer be an issue. |
THIS!
Slowly depress the pedal, hold (close bleeder if not using a bleeding bottle) then slowly let the pedal back up. |
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iowegian 
Samba Curmudgeon
Joined: February 16, 2005
Posts: 9829
Location: Somewhere between Dubuque and Keokuk
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| Posted: Sun Mar 19, 2023 7:16 am Post subject: Re: Brand new master cylinder; still no pedal. |
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| It sounds like the master cylinder was the problem all along. |
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heimlich
VWNOS.com
Joined: November 20, 2016
Posts: 6588
Location: Houston, Texas
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| Posted: Sun Mar 19, 2023 7:48 am Post subject: Re: Brand new master cylinder; still no pedal. |
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If you are getting a pedal have someone help you. Open the valve. Push the pedal. Close the valve. They let go of the pedal. Do this for all 4 wheels twice. Do them in the same order both times. I just go around the car twice in the same order.
You shouldn't pump the pedal as it creates air bubbles. Just have your helper slowly press the pedal down and hold it until you close the valve.
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esde
Samba Member
Joined: October 20, 2007
Posts: 5961
Location: central rust belt
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| Posted: Sun Mar 19, 2023 8:31 am Post subject: Re: Brand new master cylinder; still no pedal. |
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| heimlich wrote: |
| You shouldn't pump the pedal as it creates air bubbles. Just have your helper slowly press the pedal down and hold it until you close the valve. |
I don't think this is a great way to explain it
I get what you're saying, but to play the devils advocate..
pumping the pedal doesn't create bubbles. It just breaks larger bubbles that are already in the system into smaller bubbles. But brake fluid is designed to deal with this, and is extremely resistant to foaming, and does not absorb air.
I honestly don't know if 1 big bubble somewhere is better or worse to bleed out than a hundred small ones. But I do know from experience that air bubbles can get "stuck" in spots, and pumping the pedal quickly is what will get the bubble dislodged and to the end of the line where the bleeder is. One modern cars load sensing valves and ABS modules are common places for air to get trapped, and if you try bleeding them with gentle steady pressure you'll never get the air out.
I'm glad to hear he got this fixed, hopefully WW will cough up some store credit for the bad master.
SD
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Sigurd
Samba Member
Joined: April 18, 2006
Posts: 2639
Location: Rockford, IL
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| Posted: Sun Mar 19, 2023 12:27 pm Post subject: Re: Brand new master cylinder; still no pedal. |
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Well no, it's not fixed yet. The pedal is very low, and the shoes are still adjusted tight to the drums. When I back them off, I'm sure the pedal will hit the floor.
I had read both opinions about stabbing the pedal. First, don't do it because it makes tiny bubbles, or do it because it dislodges bubbles from the sides of the cylinder and seals the seals. At this point, I'm willing to try anything.
It still seems to me that if the system is properly bled and the shoes are tight to the drums, that there shouldn't be much pedal movement before it stops hard. I'm not seeing it yet, but this is a step in the right direction. |
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Glenn
Mr. 010
Joined: December 25, 2001
Posts: 76884
Location: Sneaking up behind you
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Sigurd
Samba Member
Joined: April 18, 2006
Posts: 2639
Location: Rockford, IL
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| Posted: Sun Mar 19, 2023 7:49 pm Post subject: Re: Brand new master cylinder; still no pedal. |
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| Thanks for the suggestion, Glenn, but I've been doing the same thing with my air compressor and modified reservoir cap. |
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Sigurd
Samba Member
Joined: April 18, 2006
Posts: 2639
Location: Rockford, IL
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| Posted: Sun Mar 19, 2023 7:54 pm Post subject: Re: Brand new master cylinder; still no pedal. |
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I didn't get too much done today, another useless round of pressure bleeding. But I need to confirm a few things. At this point, and after 5 pages, there a stupid mistake somewhere:
At no point should there be brake fluid on the outside of a wheel cylinder, correct? I have a boot that is not full, but wet where it touches the cylinder body.
At no point should there be brake fluid pooling inside the bottom of the backing plate, correct?
Do I need to have the reservoir cap on when I'm bleeding the brakes?
I think I have at least one leaking cylinder. |
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esde
Samba Member
Joined: October 20, 2007
Posts: 5961
Location: central rust belt
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| Posted: Sun Mar 19, 2023 8:58 pm Post subject: Re: Brand new master cylinder; still no pedal. |
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The system should be completely dry. Fluid under the dust boot or running down the backing plate is the smoking gun..
It helps keep things clean if you have the reservoir cover on, but it isn't critical. Sometimes when pumping the pedal, the release of brake line pressure between pedal strokes can cause the fluid to burp a little. If you have the cover off you might get some fluid spray.
You're on the trail now..
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modok wrote:
Bent cranks are silent but gather no moss. I mean, ah, something like that. |
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viiking
Samba Member
Joined: May 10, 2013
Posts: 2668
Location: Sydney Australia
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| Posted: Sun Mar 19, 2023 11:40 pm Post subject: Re: Brand new master cylinder; still no pedal. |
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Go back to your very first post.
You say that you have 1/4" of clearance between the pushrod and the MC piston. Is that still the case?
This is too much. You need 1mm (0.04" or 40 thou) of pushrod clearance to give you the correct free play of 5-7mm (3/16-9/32) at the pedal.
One quarter of an inch equates to a minimum of ~1&1/4" of free play at the pedal of "nothingness". That is part of the problem.
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Sigurd
Samba Member
Joined: April 18, 2006
Posts: 2639
Location: Rockford, IL
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| Posted: Mon Mar 20, 2023 6:19 am Post subject: Re: Brand new master cylinder; still no pedal. |
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| viiking wrote: |
Go back to your very first post.
You say that you have 1/4" of clearance between the pushrod and the MC piston. Is that still the case?
This is too much. You need 1mm (0.04" or 40 thou) of pushrod clearance to give you the correct free play of 5-7mm (3/16-9/32) at the pedal.
One quarter of an inch equates to a minimum of ~1&1/4" of free play at the pedal of "nothingness". That is part of the problem. |
The way I worded it is misleading. That's 1/4" at the pedal. |
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Sigurd
Samba Member
Joined: April 18, 2006
Posts: 2639
Location: Rockford, IL
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| Posted: Mon Mar 20, 2023 6:20 am Post subject: Re: Brand new master cylinder; still no pedal. |
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| Also, is there any possible way that the shoes or springs themselves could have anything to do with this? No, because they're locked up tight to the drums, right? |
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Cusser
Samba Member
Joined: October 02, 2006
Posts: 31352
Location: Hot Arizona
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| Posted: Mon Mar 20, 2023 7:56 am Post subject: Re: Brand new master cylinder; still no pedal. |
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| esde wrote: |
| The system should be completely dry. Fluid under the dust boot or running down the backing plate is the smoking gun. |
THIS !!!!
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Sigurd
Samba Member
Joined: April 18, 2006
Posts: 2639
Location: Rockford, IL
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| Posted: Mon Mar 20, 2023 8:33 am Post subject: Re: Brand new master cylinder; still no pedal. |
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| Yeah. Seeing fluid where I shouldn't see fluid set me back a little. I thought I had addressed all that. It's seeping somewhere. Time for new cylinders, I think. |
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heimlich
VWNOS.com
Joined: November 20, 2016
Posts: 6588
Location: Houston, Texas
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| Posted: Mon Mar 20, 2023 8:34 am Post subject: Re: Brand new master cylinder; still no pedal. |
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| Sigurd wrote: |
| Yeah. Seeing fluid where I shouldn't see fluid set me back a little. I thought I had addressed all that. It's seeping somewhere. Time for new cylinders, I think. |
As old as they are I would. It will bring everything up to new as well.
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Classic Brands. Classic Quality.
Not all parts are made the same. NOS OE/OEM parts made mainly in West Germany, Early Germany, and Early Brazil are where VW produced the best quality parts and best fitting products.
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Sigurd
Samba Member
Joined: April 18, 2006
Posts: 2639
Location: Rockford, IL
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| Posted: Mon Mar 20, 2023 8:36 am Post subject: Re: Brand new master cylinder; still no pedal. |
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| heimlich wrote: |
| Sigurd wrote: |
| Yeah. Seeing fluid where I shouldn't see fluid set me back a little. I thought I had addressed all that. It's seeping somewhere. Time for new cylinders, I think. |
As old as they are I would. It will bring everything up to new as well. |
5 years? And never having been used? I'm really surprised by that, but I can't argue with the fact that something's leaking. |
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mukluk
Samba Member
Joined: October 18, 2012
Posts: 7018
Location: Clyde, TX
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| Posted: Mon Mar 20, 2023 9:21 am Post subject: Re: Brand new master cylinder; still no pedal. |
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| Sigurd wrote: |
| 5 years? And never having been used? I'm really surprised by that, but I can't argue with the fact that something's leaking. |
Or you could pull them off for a good disassemble, clean and inspect, lube and reassemble, then reinstall to see if they can be put back into service to get some use out of them. All it'll take is your time. Worst case scenario is you end up replacing them anyway.
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Sigurd
Samba Member
Joined: April 18, 2006
Posts: 2639
Location: Rockford, IL
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| Posted: Mon Mar 20, 2023 10:05 am Post subject: Re: Brand new master cylinder; still no pedal. |
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| mukluk wrote: |
| Sigurd wrote: |
| 5 years? And never having been used? I'm really surprised by that, but I can't argue with the fact that something's leaking. |
Or you could pull them off for a good disassemble, clean and inspect, lube and reassemble, then reinstall to see if they can be put back into service to get some use out of them. All it'll take is your time. Worst case scenario is you end up replacing them anyway. |
Thanks for the suggestion. I did exactly that about a month ago. The insides of the cylinders didn't look that bad and the rubber was pliable. Clearly, there's still something wrong. |
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Mike Fisher
Samba Member
Joined: January 30, 2006
Posts: 17969
Location: Eugene, OR
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| Posted: Mon Mar 20, 2023 12:19 pm Post subject: Re: Brand new master cylinder; still no pedal. |
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| Sigurd wrote: |
| mukluk wrote: |
| Sigurd wrote: |
| 5 years? And never having been used? I'm really surprised by that, but I can't argue with the fact that something's leaking. |
Or you could pull them off for a good disassemble, clean and inspect, lube and reassemble, then reinstall to see if they can be put back into service to get some use out of them. All it'll take is your time. Worst case scenario is you end up replacing them anyway. |
Thanks for the suggestion. I did exactly that about a month ago. The insides of the cylinders didn't look that bad and the rubber was pliable. Clearly, there's still something wrong. |
Probably need new rubber cups/rebuild kits to put in them if they are still leaking.
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wdfifteen
Samba Member
Joined: January 26, 2019
Posts: 528
Location: Ohio
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| Posted: Mon Mar 20, 2023 12:21 pm Post subject: Re: Brand new master cylinder; still no pedal. |
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| Glenn wrote: |
| Get a power bleeder. You fill it with brake fluid, pressurize it, open the bleeder and wait for the fluid to run clean and no bubbles. Then move on to the next. |
I have a Motive power bleeder and it's a great tool. Since I use different brake fluid in different cars I don't put the fluid in the tank. I just use it to pressurize the brake system. You need to keep a close eye on the fluid level in the reservoir.
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