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63 Bug Brake bleeding
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59ragfan
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PostPosted: Fri Mar 05, 2021 2:55 pm    Post subject: 63 Bug Brake bleeding Reply with quote

What am I doing wrong?? I'm rebuilding the stock drum brakes and I replaced everything with new hard lines, hoses, MC, and wheel cylinders and reservoir. For what ever reason I cannot get the brake fluid past the master cylinder. I've tried pumping the pedal, the mytivac hand pump and a pneumatic vacuum bleeder and still no fluid at any of the wheels and no pressure in the system. The MC is full of fluid and the pressure causes the fluid to leak out were the reservoir connects. I have to be doing something wrong, it shouldn't be this hard to get the fluid to the wheels Confused

Any suggestions to get the fluid moving??
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sjbartnik
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PostPosted: Fri Mar 05, 2021 3:04 pm    Post subject: Re: 63 Bug Brake bleeding Reply with quote

Sounds like possibly your brake pedal push rod is adjusted incorrectly and thus the piston inside the master cylinder is blocking the compensating ports, which would keep fluid from getting into the system.

You need to have 1mm of space between the end of the push rod and the piston in the m/c with the brake pedal at rest. You cannot measure this directly, but you can measure the amount of pedal movement before the push rod hits the piston. If you use your hand to move the pedal and not your foot, you can feel it. You should have about 5-7mm of free movement at the pedal before you feel the push rod make contact with the piston.

If the push rod is too long, or the pedal stop on the floor is adjusted incorrectly, the m/c piston cannot return to rest position and fluid will not be able to flow from reservoir through m/c to the wheels.

Ideally you're not supposed to adjust the push rod length directly at all, but sometimes with replacement master cylinders and who knows how it's been fucked over the years, you have no choice. But your first effort should be to see if you can get the play correct using the pedal stop on the floor rather than adjusting the push rod length.
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wheel607
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PostPosted: Fri Mar 05, 2021 3:05 pm    Post subject: Re: 63 Bug Brake bleeding Reply with quote

There should be NO LEAKS where the reservior connects , regardless of the pressure used with the assist unit. You are sucking in air, and no pressure is going up the lines to the wheel cylinders. First things first.......you have to get this fixed before you continue. Tighten, then tighten more on CLAMPS, until you no longer have any leaks. Always use clamps, regardless of what others may say.
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MrGoodtunes
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PostPosted: Sat Mar 06, 2021 2:24 pm    Post subject: Re: 63 Bug Brake bleeding Reply with quote

sjbartnik wrote:
Sounds like ... You need to have 1mm of space between the end of the push rod and the piston in the m/c with the brake pedal at rest ...


See dimension "S" in this diagram:

Image may have been reduced in size. Click image to view fullscreen.
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viiking
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PostPosted: Sun Mar 07, 2021 4:01 pm    Post subject: Re: 63 Bug Brake bleeding Reply with quote

I agree with the others that it could be the pushrod. Normally you shouldn't play with it.I agree that you should have the relevant clearance as determined by hand. This is adjusted at the floor plate not the pushrod.

So these questions are important before you compound the error and start fiddling with the pushrod.

1. How were the brakes before you overhauled them? Did the brakes get fluid before? If so then it is unlikely to be your pushrod dimension.

2. Do you have a single or dual circuit MC? What did you have before?

3. Have you considered that the new MC is a piece of Chinese junk and is defective out of the box? What brand is it?
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59ragfan
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PostPosted: Mon Mar 08, 2021 11:58 am    Post subject: Re: 63 Bug Brake bleeding Reply with quote

Thanks for the great responses!

When I got the car the brakes pedal went to the floor so I replaced everything. I discovered that all the fluid had leaked out of the wheel cylinders and the system was dry as a bone.

The new MC is a single circuit TRW. Same as original I replaced. I have considered it might be the problem but I'm stubborn and don't want to go thru the trouble of replacing it. Wink Wolfsberg West has a worning with its MC, stating you need a power bleeder when replacing the the MC. Anyone had experience with using a Power bleeder?

I adjusted the pedals and pushrod per the diagram mrgoodtunes posted (thanks!). Still no fluid to the pedals, no pressure in the system.

Maybe I'll open all the bleeders and let gravity do the work. My new theory is that all the air in the system might be preventing the fluid to flow. Idea
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toxicavenger70
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PostPosted: Tue Mar 09, 2021 12:07 pm    Post subject: Re: 63 Bug Brake bleeding Reply with quote

I had a huge issue bleeding my brakes when I installed all new hard lines and braided brake lines. What I (and my VW shop) figured out is where the hard (metal) brake lines were screwed into the rubber lines there was still a air gap between the feral end and the cupped end. You could actually take the metal line and move it a 1/6" of an inch side to side. Which keeps the brake lines from sealing. If they do not seal you can not build up pressure.

I have posted a pic of the web. I hope it explains what I mean. Or I might be confusing the crap out of you. lol
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thomas.
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PostPosted: Thu Mar 11, 2021 2:12 am    Post subject: Re: 63 Bug Brake bleeding Reply with quote

Before attempting to bleed , 1st. adjust all brake shoes all the way out ( locked )against all four drums.
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59ragfan
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PostPosted: Thu Mar 11, 2021 6:11 pm    Post subject: Re: 63 Bug Brake bleeding Reply with quote

Success!! kinda. I finally was able to get fluid to the wheels, but it wasn't easy... It wasn't one problem but many. Thanks for everyone's feedback it appears everyone was correct at diagnosing the problems, cigars for the winners!

First I adjusted the push rod and pedals out all the way out because I could tell when it was hitting the MC with no pressure in the line. Now fluid was flowing, Fix #1

I used the piece of junk Mytivac vacuum pump but the fittings leaked so much air it was useless. To stop the leaks I put teflon tape on the bleeder screws, greased the rubber fitting and put a zip tie on the fitting to tighten it against the bleeder screw. That worked! I was able to hold vacuum and open the bleeders, starting at the right rear tire as recommended by VW. It took forever but fluid started flowing at the wheels. Fix #2 The stupid mytyvac leaked fluid all over the place as a bonus....

Between bleeding each wheel I tried to pump the pedal to build pressure, nothing, right to the floor every time even after bleeding all 4 wheels. I'm guessing a bad master cylinder and new right out of the box. Rolling Eyes Hope fully Fix#3

Next step replace the master cylinder, the one thing I was trying to avoid....
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toxicavenger70
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PostPosted: Fri Mar 12, 2021 1:33 pm    Post subject: Re: 63 Bug Brake bleeding Reply with quote

59ragfan wrote:
Success!! kinda. I finally was able to get fluid to the wheels, but it wasn't easy... It wasn't one problem but many. Thanks for everyone's feedback it appears everyone was correct at diagnosing the problems, cigars for the winners!

First I adjusted the push rod and pedals out all the way out because I could tell when it was hitting the MC with no pressure in the line. Now fluid was flowing, Fix #1

I used the piece of junk Mytivac vacuum pump but the fittings leaked so much air it was useless. To stop the leaks I put teflon tape on the bleeder screws, greased the rubber fitting and put a zip tie on the fitting to tighten it against the bleeder screw. That worked! I was able to hold vacuum and open the bleeders, starting at the right rear tire as recommended by VW. It took forever but fluid started flowing at the wheels. Fix #2 The stupid mytyvac leaked fluid all over the place as a bonus....

Between bleeding each wheel I tried to pump the pedal to build pressure, nothing, right to the floor every time even after bleeding all 4 wheels. I'm guessing a bad master cylinder and new right out of the box. Rolling Eyes Hope fully Fix#3

Next step replace the master cylinder, the one thing I was trying to avoid....

Before I would replace it would try to bench bleed the master cylinder. Then start bleeding from the passenger rear tire, driver's rear, passenger front and then the left front.
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sjbartnik
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PostPosted: Fri Mar 12, 2021 2:58 pm    Post subject: Re: 63 Bug Brake bleeding Reply with quote

I have had problems using MityVac to bleed the brakes, especially for drum brakes. As you found, it can pull air past the threads on the bleeder screw, but it may also be able to pull air in via the seals inside the wheel cylinder, meaning you'll always be pulling new air in.

Now that you have fluid to the wheels, bleed the rest of the way either the old fashioned way, with a helper to pump the pedal, or spring for a Motive bleeder - that thing is dope.
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59ragfan
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PostPosted: Mon Apr 12, 2021 2:23 pm    Post subject: Re: 63 Bug Brake bleeding Reply with quote

Update - Bench bled and replaced the master cylinder with a German MC. Went to bleed the system and the front right wheel cylinder started leaking, but it would build a little pressure at the pedal about 25%. Replaced both front wheel cylinders with German parts. The rod from the pedal to the MC was to long so I shortened it 1/4". I wasn't able to adjust the pedal for the proper free play. I compared it to my buddies from his '62 and was longer.

Its gets really weird now, I've bled all the wheels in the proper order with pumping the pedal and the mytivac till the fluid runs clear, no bubbles. I'm on my 3rd bottle of brake fluid. The pedal still goes to the floor and will not build pressure!

There is no leaking any ware but it feels like air is getting in somehow??

Anymore suggestions?
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toxicavenger70
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PostPosted: Mon Apr 12, 2021 7:37 pm    Post subject: Re: 63 Bug Brake bleeding Reply with quote

59ragfan wrote:
Update - Bench bled and replaced the master cylinder with a German MC. Went to bleed the system and the front right wheel cylinder started leaking, but it would build a little pressure at the pedal about 25%. Replaced both front wheel cylinders with German parts. The rod from the pedal to the MC was to long so I shortened it 1/4". I wasn't able to adjust the pedal for the proper free play. I compared it to my buddies from his '62 and was longer.

Its gets really weird now, I've bled all the wheels in the proper order with pumping the pedal and the mytivac till the fluid runs clear, no bubbles. I'm on my 3rd bottle of brake fluid. The pedal still goes to the floor and will not build pressure!

There is no leaking any ware but it feels like air is getting in somehow??

Anymore suggestions?

Unfortunately it sounds like you have a leak somewhere. I would revisit every line to make sure they are all tight. Here is the actually pics of my issue. I wish I would have taken a video to show my issue.
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cory464
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PostPosted: Fri Apr 16, 2021 11:51 am    Post subject: Re: 63 Bug Brake bleeding Reply with quote

59ragfan wrote:
Update - Bench bled and replaced the master cylinder with a German MC. Went to bleed the system and the front right wheel cylinder started leaking, but it would build a little pressure at the pedal about 25%. Replaced both front wheel cylinders with German parts. The rod from the pedal to the MC was to long so I shortened it 1/4". I wasn't able to adjust the pedal for the proper free play. I compared it to my buddies from his '62 and was longer.

Its gets really weird now, I've bled all the wheels in the proper order with pumping the pedal and the mytivac till the fluid runs clear, no bubbles. I'm on my 3rd bottle of brake fluid. The pedal still goes to the floor and will not build pressure!

There is no leaking any ware but it feels like air is getting in somehow??

Anymore suggestions?




if you havent done so, adjust the shoes all the way out until the drums are locked. then bleed the system and back the shoes off slightly.
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59ragfan
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PostPosted: Tue Sep 27, 2022 11:43 am    Post subject: Re: 63 Bug Brake bleeding Reply with quote

cory464 is absolutely correct. Adjusting the shoes all the way out solved the problem.

But a great discussion on drum brakes and how to make them work!
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