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It seems as though I'm manually bleeding my brakes every other month but now, I have virtually no pedal.  I put on a new master cylinder a couple of months ago and pulled my rear drums and replaced them with discs some time ago.  I get a good fluid-flow when I press the pedals with no indication of air.  I've also checked for weeping along my lines.  I'm thinking faulty M/C and wondering about replacing it. I am certainly open to suggestions in regards to repairs HELP!!!

meade

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This the disc brake master cylinder I buy for all conversions.. I also buy 90% of my VW related parts form Jack at Bug Stuff in PA for the last 30 years .   https://www.bugstuffonline.com...der-for-disc-brakes/

I also buy from some parts from Appletree VW   https://www2.cip1.com/ProductD...ductCode=C13-16-9554

Last edited by Alan Merklin
@Meade posted:

I didn’t realize that it needed specific bore. I just used a stock master cylinder. Does a MC need to be bled and if so, how?

Meade

You can and probably should fill and bleed it on a bench before installing. Clamp the flange in a vice securely with the MC level. Put a reservoir on top—get the kind that just plugs into both soft leads. Plug in the senders and block all the ports except the ports in each that will be used to feed fluid to the brakes. Screw short brake lines with fittings into those, curl the lines up and feed them back into the top of the reservoir.

Now fill the reservoir with new brake fluid from an unopened can.

Gently push in the plunger using a metal rod with a rounded tip, or a big phillips screwdriver, being careful not to slip off the indent and mess up the seal.

In a few rounds you'll be pumping fluid through the unit. You'll see it's not blowing air.

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If you can, suck the fluid out of the reservoir before unplugging it. If you can't do that, just take the whole thing out of the vice and pull the res off over a trash can.

Plug the top holes to keep the fluid in. Be quick when you install the MC.

You still have to bleed the system but it should be less arduous.

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What Ed said. I put a new Super Beetle M/C on my Spyder last year and the first time I did it, I didn't bench bleed it. It took me the better part of two afternoons to get decent pedal.  

I had to pull it and reinstall it and the second time it took about ten minutes after bench bleeding it prior to install.



But i think Alan hit the nail on the head. You need a higher capacity M/C to push the pistons in disc brakes.



PS: My son the motorcycle mechanic helped me bleed my brakes both times.   He taught me a little trick: tapping on the M/C between pumps. I guess it helps break loose little air bubbles that are clinging to the sides of the bore.  

Last edited by dlearl476

I'll admit I have poor work pace organizational skills, no matter how good my intentions are to maintain a clean area, the day is kaput when discovery is made that the 10mm has once again done the disappearing act. These work ethics are not something that I acquired from my late dad who was a highly detailed Tool and Die maker who would never have more than three tools at any given time vacate his tool box hence, we did not play well together. He never got to see a single one of my car projects.

Last edited by Alan Merklin

Funny! I knew Alan was a brotha from and anotha mutha.

My brother and I are polar opposites. I typically try to do too much so the workspace looks like it had a Soviet air strike. I'm sure the mimosas and bloody Marys don't help.  I don't mind because my grandfather (a machinist) did the same thing. My brother is super clean -almost to the level of being museum quality -just sickening. But, his work is impeccable so there must be something to it. I'm more of a "Passenger door, naaa, that's extra. We'll go with out it." Life is too short to be hampered by arranging your sockets alphabetically by height.

Once upon a time I could instantly remember where I put down a tool and return to it.

Once upon a time I could also remember a couple of hundred 9-digit part numbers, people's phone numbers or email addresses, license plate numbers for several days, books I had read years ago - Important stuff like that.

Not any more.

Now, if I don't force myself to put tools in a carry tray they seem to walk, I can't even remember my daughter's phone number (fortunately, my phone does and shows me her name) and I have no clue what the license plate on my speedster says.

None of this stuff bothers me.  It's been a pretty crazy 70 years, and I'm looking forward to the next 30 or 40.  Always looking forward, seldom looking back.

When I'm working on a project that takes more than a day I tend to generate piles of stuff (tools, fasteners, parts, etc.) in several places in the garage.  Somehow I know which pile to go to for a particular wrench or bolt even a week later.  I may not remember where I left my glasses a minute ago, but I can find that socket that I need - even a 10mm one!

Last edited by Lane Anderson

When I'm working on a project that takes more than a day I tend to generate piles of stuff (tools, fasteners, parts, etc.) in several places in the garage.  Somehow I know which pile to go to for a particular wrench or bolt even a week later.  I may not remember where I left my glasses a minute ago, but I can find that socket that I need - even a 10mm one!

I used to brag about having all my 10mm sockets. I did the fluids in one of my ML's the other day and my 3/8 drive 10mm Allen that I needed for the differentials was nowhere to be found.

Had to resort to the crescent wrench on an Allen wrench workaround.

Funny story: Years ago I had an Audi 5000 CS Quattro 4DSD. The clutch was physically fine, but I couldn't tell if the hydraulic master or slave was bad. So I replaced both. The master was a really LARGE pain to change. The slave was pretty easy.

I tried bleeding it with a vacuum bleeder by myself. I tried bleeding it with a pressure bleeder by myself. No pedal. Then I got a friend's help to bleed it the old fashioned way. It came right up, like it should. After the job was finished, I couldn't find my 7mm combination wrench. I guess I left it at my buddy's house where we changed the parts, oh well.

I found it a year later when I was under there looking at the exhaust or something. It was still on the bleeder!

I'm not sure if this applies to your bleeding problem, but I recently replaced a master cylinder and had a problem bleeding and getting good pedal pressure.  Turned out that I just needed to adjust the rod, that presses the master cylinder piston (attached to the brake pedal).  It was turned in so far that the pedal was almost to the floor before it even contacted the master cylinder piston. I turned it out so the pedal only had to be depressed about 1/4" inch before it started to press the MC piston.   Then I rebled all four wheels and had a full pedal with great breaks.

Last edited by Troy Sloan
@Troy Sloan posted:

I'm not sure if this applies to your bleeding problem, but I recently replaced a master cylinder and had a problem bleeding and getting good pedal pressure.  Turned out that I just needed to adjust the rod, that presses the master cylinder piston (attached to the brake pedal).  It was turned in so far that the pedal was almost to the floor before it even contacted the master cylinder piston. I turned it out so the pedal only had to be depressed about 1/4" inch before it started to press the MC piston.   Then I rebled all four wheels and had a full pedal with great breaks.

The Bentley VW Service Manual tells you NOT to adjust that rod, that it comes pre-set from the factory, but then again, why make it adjustable if they don't want you to do it, right? I can bet you that the vast majority of these cars have been messed with in the last 40 plus years and more that the donor pans were rolling around.

Bentley tells you not to adjust the rod in a Beetle , they didn't know about Replicas back in the day . Adjustments are necessary when the pedal stop is moved, warn etc. You adjust the rod so that there is a just a " click " ( 1/16") between the pedal in the rest position and rod contact with the master cylinder piston. This free play adjustment assures that the rod is in the rest position. w/o out that free play, you can bleed endlessly without success.

Bentley tells you not to adjust the rod in a Beetle , they didn't know about Replicas back in the day . Adjustments are necessary when the pedal stop is moved, warn etc. You adjust the rod so that there is a just a " click " ( 1/16") between the pedal in the rest position and rod contact with the master cylinder piston. This free play adjustment assures that the rod is in the rest position. w/o out that free play, you can bleed endlessly without success.

Great point, Alan. Thanks!

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