I have not been able to get the brakes on my '72 411 4 door to come up to snuff. Pretty much everything has been replaced with no change in performance. I always have to pump the pedal a couple of times to get a good pedal feel. The back shoes are adjusted up as tight as I can reasonably run them and the front pads have just the normal light drag when you spin the rotors. There is no throbbing of the pedal when braking and no tendencey to lock either the front or rear when braking hard, just a pedal that goes almost to the floor on the first pump. I have probably bled a full quart of fluid through the system with no positive affect. The following stuff has all been replaced with no change in braking.
Master cylinder
Hoses from reservoir to master cylinder
Rebuild front calipers with new pads
Turned rotors
All flexible hoses replaced
Rear slave cylinders
Rear shoes
Turned rear drums
Any suggestions would be appreciated
411 brakes
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raygreenwood
- Posts: 11912
- Joined: Wed Jan 22, 2003 12:01 am
Ok. A couple things.
Make sure the handbrake is off. And as you noted, make sure the rear brakes are nicely adjusted. The reason for this, is that putting the handbrake on instead of adjustingt the rear shoes...allows the pistons in a poorly adjusted system to more toward the ends of their bores. This makes the volume necessary for the master cylinder to pump...larger...and slows down the bleeding process.
Also, wheredid you get the new master cylinder? If it is NOS...it is suspect. Here is a test for it. Pump up the brakes. Hold them tight so they have pressure. Release "some" pressure with your foot..but do not take your foot off the pedal. Immediatly re-apply pressure hard. If the pedal sinks somewhat...either your master cylinder seals are shot...or something is blocking acompensating port flap valve open. This will either be debris like dust...or corrosion (very common in NOS units). This can happen in NOS cylinders that have been on the shelf.
Did you disassemble the master cylinder and wash everything in alcohol before using? This is 100% required on even brand new master cylinders. Its amazing how much crud gets in from the assembly floor.
When you dissasemble the cylinder, you do not need to remove all of the seals. But you must remove the bottom seal near each spring and make sure there is not dust or green corrosion under the brass flap valves. I polish both the brass flap valve and teh surface on teh piston with the holes in it...where it seats...with 2000 grit sandpaper....nothing courser. You can get that at Pep boys in the body work department.
If you rebuilt your cylinder yourself......and you honed it...and left honing hatch marks...you must remove those with either 000 steel wool or 1500-2000 grit sandpaper. There should be no honing marks in any brake cylinder. It destroys the sealing surface for the cups. If you left any rust pits...those will be a problem.
Also, only bleed the front calipers by the top bleeder valve. Also, the fronts and the rears are very susceptible to air being sucked back in around the threads during bleeding. Remove all bleeder valves and wrap a very small amount of teflon tape onto the threads. Then..when bleeding...only crack them open maybe 1/4 turn. The 411/412 brake system is very "circuitous". In the high spots, air bubbles have a habit of allowing fluid to bypass them...so you never get all the air out of the system. It bleeds better when high pressure can be delivered..AND...when you pump very slowly. So...if you crack teh bleeder valves barely open...it builds pressure AND allows you to pump slowly. You need to start on teh right rear wheel, then the left rear wheel, right front, then left front. It will take at least 5 rounds of this.
Also, make very sure that your brake pedal is properly adjusted. If it is too tight and does not fully come out of contact with the piston...you will have problems.
Once you get all of this done, generally a couple days of driving should be followed by another round of bleeding. Ray
Make sure the handbrake is off. And as you noted, make sure the rear brakes are nicely adjusted. The reason for this, is that putting the handbrake on instead of adjustingt the rear shoes...allows the pistons in a poorly adjusted system to more toward the ends of their bores. This makes the volume necessary for the master cylinder to pump...larger...and slows down the bleeding process.
Also, wheredid you get the new master cylinder? If it is NOS...it is suspect. Here is a test for it. Pump up the brakes. Hold them tight so they have pressure. Release "some" pressure with your foot..but do not take your foot off the pedal. Immediatly re-apply pressure hard. If the pedal sinks somewhat...either your master cylinder seals are shot...or something is blocking acompensating port flap valve open. This will either be debris like dust...or corrosion (very common in NOS units). This can happen in NOS cylinders that have been on the shelf.
Did you disassemble the master cylinder and wash everything in alcohol before using? This is 100% required on even brand new master cylinders. Its amazing how much crud gets in from the assembly floor.
When you dissasemble the cylinder, you do not need to remove all of the seals. But you must remove the bottom seal near each spring and make sure there is not dust or green corrosion under the brass flap valves. I polish both the brass flap valve and teh surface on teh piston with the holes in it...where it seats...with 2000 grit sandpaper....nothing courser. You can get that at Pep boys in the body work department.
If you rebuilt your cylinder yourself......and you honed it...and left honing hatch marks...you must remove those with either 000 steel wool or 1500-2000 grit sandpaper. There should be no honing marks in any brake cylinder. It destroys the sealing surface for the cups. If you left any rust pits...those will be a problem.
Also, only bleed the front calipers by the top bleeder valve. Also, the fronts and the rears are very susceptible to air being sucked back in around the threads during bleeding. Remove all bleeder valves and wrap a very small amount of teflon tape onto the threads. Then..when bleeding...only crack them open maybe 1/4 turn. The 411/412 brake system is very "circuitous". In the high spots, air bubbles have a habit of allowing fluid to bypass them...so you never get all the air out of the system. It bleeds better when high pressure can be delivered..AND...when you pump very slowly. So...if you crack teh bleeder valves barely open...it builds pressure AND allows you to pump slowly. You need to start on teh right rear wheel, then the left rear wheel, right front, then left front. It will take at least 5 rounds of this.
Also, make very sure that your brake pedal is properly adjusted. If it is too tight and does not fully come out of contact with the piston...you will have problems.
Once you get all of this done, generally a couple days of driving should be followed by another round of bleeding. Ray
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wildthings
- Posts: 1171
- Joined: Thu Jun 03, 2004 12:42 am
Ray this is definitely happening. The master cylinder was NOS that had been carefully stored. I took it apart before installing it and there was no sign of corrosion and the seals and surfaces looked perfect. Will pull it off again and check the compensating port for cleanliness. I find it strange that the new master cylinder exhibits exactly the same symptoms as the old, which also appeared spotless inside when disassembled. Both new and old were the same brand though at present I can't remember the brand name.Also, wheredid you get the new master cylinder? If it is NOS...it is suspect. Here is a test for it. Pump up the brakes. Hold them tight so they have pressure. Release "some" pressure with your foot..but do not take your foot off the pedal. Immediatly re-apply pressure hard. If the pedal sinks somewhat...either your master cylinder seals are shot...or something is blocking acompensating port flap valve open. This will either be debris like dust...or corrosion (very common in NOS units). This can happen in NOS cylinders that have been on the shelf.
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vwbill
- Posts: 970
- Joined: Sat Feb 15, 2003 12:01 am
It is very frustating getting a good peddle on our cars! It takes a lot of bleeding!! Ray has a great idea for the bleeder nipple issue! I have too wedge a 2x4 against the seat front rod and the brake peddle after pumping it up and then just cracking the nipples all around the car after hand vacuum pump bleeding. I have to do alot of the under the car back to the brake peddle till I have worn my shoulder out,lol! Then you have to drive and then repeat then wait a week and repeat,lol! I wonder if the Ray vanagon master and disc brake all around setup would be sweet? I wonder how they did it at the dealer? bill
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raygreenwood
- Posts: 11912
- Joined: Wed Jan 22, 2003 12:01 am
The problem with NOS cylinders..is simply age. The rubber of the seals can harden to a durometer as high as 15% more than original...just by sitting still. They take a "set". It can cause the cups to collapse after inflating...with a slight decrease in pressure. If teh cylinder is new...it may be worth further investment ....like getting a type or rabbit cylinder of the same make...and stealing the seals only. Ray
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can86
- Posts: 87
- Joined: Wed Sep 01, 2004 1:34 pm
I have the same car and will be doing a brake job this spring in order to get the car on the road. All i have right now is rebuilt calipers, new pads & shoes, and will be getting the rotors and drums cleaned up... I also have to make a new line for one of the front sides. The only parts i'm not 100% sure on is the master cylinder and i geuss cleaning out the system?? This car has been sitting for a number of years...this post helps alot!
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wildthings
- Posts: 1171
- Joined: Thu Jun 03, 2004 12:42 am
I finally got a little more air out of the rear cylinders, enough to make the car safe to drive, but not as good as it should be. I think that part of the problem is that the fluid exits the top of the master cylinder and then the tubes go up for a inch and a half before heading down. I know from experience that brakes work better when the lines come out of the side or bottom of a cylinder and then head downward, so that air will naturally work its way back up to and out of the master cylinder on its own. It is real easy for air to get caught in the upward bends of the flex lines at each wheel as well. I think that I might take a 30cc syringe and use it to force fluid in through the bleeders and out through the master cylinder to see if trapped air can be forced back through the master cylinder that way.
I pulled down my old master cylinder, which is the same brand, a FAG, as the new one I had put on. The FAG cylinder has no compensating port to get stuck open so I don't think my problems are apt to be dirt related.
I pulled down my old master cylinder, which is the same brand, a FAG, as the new one I had put on. The FAG cylinder has no compensating port to get stuck open so I don't think my problems are apt to be dirt related.
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raygreenwood
- Posts: 11912
- Joined: Wed Jan 22, 2003 12:01 am
Yes....all master cylinders have compensating ports...or they do not work. The compensating port is the very small port...and I mean very small....opposite the main inlet port...under the rubber bung where the reservoir tubes insert into the top. It can easily be either gummed up...or rusted over. You cannot see it unless you pop the bungs out of the top. This is a good idea. If the plastic tubes were difficult to push in....it often happens that the rubber bung is pushed in slightly too deep...covering the compensating ports. It can also be that the bungs are in upside down. That too...will cover the compensating ports.
The brass flap valves...are also sometimes labled compesation ports or valves. If any are missing...you will have big problems. Forcing fluid reverse through the system does not work....unless....the brass flap valves are leaking...and then there you have it.
But.....you are correct about the snaky way the tubing moves. It is part of the problem.
Try this instead. Get a 2x4 and a pad of something soft. Pump up the pedal..and wedge it with the 2x4 so it holds pressure. Then reach under thedash.....get a rag first....and juuuuust barely crack open the union nut for one of the brake tubes. You should see air bubble. The first ooze of fluid....seal it off. Then...do the other. Then repeat...then bleed.
Its also worth it to know...that with the barely cracked bleeders allowing you slow pumping and high pressure......when you let the pedal back up....let it up slowly...very slowly...so as to draw fluid in through that microscopic port before the piston blcoks it.
Also...its worth it to pump up your brake pedal...go back and release the bleeder valve...then close it before letting the pedal up slowly. Ray
The brass flap valves...are also sometimes labled compesation ports or valves. If any are missing...you will have big problems. Forcing fluid reverse through the system does not work....unless....the brass flap valves are leaking...and then there you have it.
But.....you are correct about the snaky way the tubing moves. It is part of the problem.
Try this instead. Get a 2x4 and a pad of something soft. Pump up the pedal..and wedge it with the 2x4 so it holds pressure. Then reach under thedash.....get a rag first....and juuuuust barely crack open the union nut for one of the brake tubes. You should see air bubble. The first ooze of fluid....seal it off. Then...do the other. Then repeat...then bleed.
Its also worth it to know...that with the barely cracked bleeders allowing you slow pumping and high pressure......when you let the pedal back up....let it up slowly...very slowly...so as to draw fluid in through that microscopic port before the piston blcoks it.
Also...its worth it to pump up your brake pedal...go back and release the bleeder valve...then close it before letting the pedal up slowly. Ray
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wildthings
- Posts: 1171
- Joined: Thu Jun 03, 2004 12:42 am
Ray ,
I was incorrect in saying that there were no compensating ports, the FAG cylinders have no compensating port valves or flabbers that can be stuck open. My orifices are clear, no problem there.
I have actually talked with several people who have set ups that force fluid in though the bleeders and out through the master cylinder. They claim it works well, so I am going to try their stuff and will report back. First I think that I will park nose down of the steepest hill I can find and try pumping it a few times to see if any of the air will work back through the master cylinder that way. There is a place in our town where one of the side streets must be 30 degrees for a short distance, that may prove to move the air around some. Don't know that I can actually park there though as it is way too steep to trust the parking brake to hold securely, and I am not about the put the auto tranny in park as I may not be able to get it out again. Maybe I can get the wife to throw chocks in front of the wheels.
I was incorrect in saying that there were no compensating ports, the FAG cylinders have no compensating port valves or flabbers that can be stuck open. My orifices are clear, no problem there.
I have actually talked with several people who have set ups that force fluid in though the bleeders and out through the master cylinder. They claim it works well, so I am going to try their stuff and will report back. First I think that I will park nose down of the steepest hill I can find and try pumping it a few times to see if any of the air will work back through the master cylinder that way. There is a place in our town where one of the side streets must be 30 degrees for a short distance, that may prove to move the air around some. Don't know that I can actually park there though as it is way too steep to trust the parking brake to hold securely, and I am not about the put the auto tranny in park as I may not be able to get it out again. Maybe I can get the wife to throw chocks in front of the wheels.
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raygreenwood
- Posts: 11912
- Joined: Wed Jan 22, 2003 12:01 am
I have dozens of both FAG and Teves (old) . There IS in both (and all) varieties of this cylinder (and very brake cylinder)....flap valves.
If your cylinder has no flap valves in it....it will not work properly...and cause the exact problem you are eperiencing...and will be dangerous....and 100% will fail one day under pressure.
To make sure we are on teh same wavelength...the flap valves on the first piston....that one located closest to the pushrod....are located under the cup...that is right down next to the spring. To service these...you must compress the spring and remove the screw in the center. Uner that spring you will find a star of "maltese cross" shaped metal washer ...crimped onto the end of the piston. Gently pry it loose. Under that will be a small metal cup. Pull that off. Then the rubber cup comes off. Under that is a brass flap valve. Looks like a thin brass washer. It covers a ring of small holes in the piston. Remove it carefully...and remember which face went against the piston. This is because usually...only one face of the valve was lapped smooth from the factory.
Polish the face that goes against the piston on a very fine wet stone or with 2000 grit paper. Polish teh face of the piston where the valve sits...the same way.
Repeat this process for the lower piston. Then clean religiously and re-assemble.
I have found more than a few cylinders that have been missing important parts from the factory. Ray
If your cylinder has no flap valves in it....it will not work properly...and cause the exact problem you are eperiencing...and will be dangerous....and 100% will fail one day under pressure.
To make sure we are on teh same wavelength...the flap valves on the first piston....that one located closest to the pushrod....are located under the cup...that is right down next to the spring. To service these...you must compress the spring and remove the screw in the center. Uner that spring you will find a star of "maltese cross" shaped metal washer ...crimped onto the end of the piston. Gently pry it loose. Under that will be a small metal cup. Pull that off. Then the rubber cup comes off. Under that is a brass flap valve. Looks like a thin brass washer. It covers a ring of small holes in the piston. Remove it carefully...and remember which face went against the piston. This is because usually...only one face of the valve was lapped smooth from the factory.
Polish the face that goes against the piston on a very fine wet stone or with 2000 grit paper. Polish teh face of the piston where the valve sits...the same way.
Repeat this process for the lower piston. Then clean religiously and re-assemble.
I have found more than a few cylinders that have been missing important parts from the factory. Ray
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wildthings
- Posts: 1171
- Joined: Thu Jun 03, 2004 12:42 am
I was able to get a much better pedal by parking on a steep hill and pumping the brakes for several minutes. The applied height of the pedal came up probably about 3/4 to 1 inch by doing this and the pedal is noticably less spongy. Hopefully if there were still any air in the rear lines this will have also moved that air to the rear cylinders and once I get time I will be able to bleed it out there.
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raygreenwood
- Posts: 11912
- Joined: Wed Jan 22, 2003 12:01 am
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MattKab
- Posts: 790
- Joined: Sat Jul 27, 2002 12:01 am
Lastnight I finished overhauling the brakes on my '70 411. It does not have the optional servo like in the Haynes manual. It was an absolute pleasure to do so.
I Rigged up an old T2 m/c with an M10 bolt to push out each of the 4 pistons in turn, I was pleased to find the pistons and bores 99% rust free. I polished off the staining with red Scotch-brite, cleaned all parts with brake/clutch cleaner and reassembled them 100% dust-free with new DOT4 fluid. All rubber parts were visibly A1 perfect.
I replaced the hard lines where needed with Kunifer and 2 new flex hoses (270mm, same as T1 rear)
I did the same with the m/c, polished the bore with the red Scotch-brite wrapped around a small bottle brush. My blue delivery hoses were still good to go.
When it came to bleeding, I had this thread in my mind. However, It went very easy, I applied ~20psi to the bottle, and used the teflon tape & 1/4 turn open and a clear tube with a pretty strong check-valve at the end.
I only needed to bleed each side once, the 'pedal' feels amazing.
Wildthings, I wish I could help you with your bleeding issue, I was anticipating some issues based on this thread.
Maybe RHD is immune from this issue? I can't see how.
'Hope youve fixed it by now,
Matt
I Rigged up an old T2 m/c with an M10 bolt to push out each of the 4 pistons in turn, I was pleased to find the pistons and bores 99% rust free. I polished off the staining with red Scotch-brite, cleaned all parts with brake/clutch cleaner and reassembled them 100% dust-free with new DOT4 fluid. All rubber parts were visibly A1 perfect.
I replaced the hard lines where needed with Kunifer and 2 new flex hoses (270mm, same as T1 rear)
I did the same with the m/c, polished the bore with the red Scotch-brite wrapped around a small bottle brush. My blue delivery hoses were still good to go.
When it came to bleeding, I had this thread in my mind. However, It went very easy, I applied ~20psi to the bottle, and used the teflon tape & 1/4 turn open and a clear tube with a pretty strong check-valve at the end.
I only needed to bleed each side once, the 'pedal' feels amazing.
Wildthings, I wish I could help you with your bleeding issue, I was anticipating some issues based on this thread.
Maybe RHD is immune from this issue? I can't see how.
'Hope youve fixed it by now,
Matt
1979 Karmann Beetle with 1.8ti T4 (still pastel yellow)
1970 411 Variant (black) daily driver
1964 lil' window Beetle (soon to be black)
1970 411 Variant (black) daily driver
1964 lil' window Beetle (soon to be black)