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stoneboys3
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Joined: June 05, 2016
Posts: 41
Location: Missouri, USA
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 Posted: Fri Dec 30, 2016 10:55 am Post subject: Replacing servo and master cylinder |
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Wolfsburg West sells a servo/master cylinder for a 71 as long as you use their '73-79 reservoir. Has anyone made this switch? and how well did it go?
Also as far as bleeding brakes after the reinstall, do I need a mechanic to bleed them, or is this something I can do from home (what's necessary equip?)
Thanks for help
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TomWesty
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Joined: November 23, 2007
Posts: 3482
Location: Wyoming,USA
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| Posted: Fri Dec 30, 2016 11:00 am Post subject: Re: Replacing servo and master cylinder |
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I'm planning on doing it, but later this summer. Also have a '71. Aeromech seems to be one of the go to guys for brakes questions. Also Colin (Amskeptic).
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alman72
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Joined: October 09, 2014
Posts: 2573
Location: MICHIGAN
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| Posted: Fri Dec 30, 2016 11:24 am Post subject: Re: Replacing servo and master cylinder |
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| quit cluttering the joint up. keep it in one general named post, or put it in the stupid question thread. If you put it in your old thread, it bumps to the top of the forum where it can be seen and folks can respond. |
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Abscate
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Joined: October 05, 2014
Posts: 22641
Location: NYC/Upstate/ROW
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| Posted: Fri Dec 30, 2016 11:49 am Post subject: Re: Replacing servo and master cylinder |
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Definitely bleed them yourself. It's an important skill that will get you in the habit if changing your fluid every two years after you wrestle with a few rusty brake parts.
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rockerarm
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Joined: December 16, 2009
Posts: 3552
Location: Los Angeles
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| Posted: Fri Dec 30, 2016 2:32 pm Post subject: Re: Replacing servo and master cylinder |
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Hi. The difference between the two components is because the openings atop the master changed which resulted in a different reservoir. The replacement master's use the later distance between the openings. Just another added expense.
I stand corrected that the reservoir differences are the location of the inlet port.
Bleeding should not hamper your efforts here as abscate stated. A couple of tips might be to use the better brake switches, as the $5 ones are failing miserably. Make sure you have sufficient master cylinder freeplay.
A couple reasons brake bleeding becomes difficult is if the bleeder fittings don't allow fluid to pass out of the caliper/wheel cyl and/or the rubber brake hoses are old and have internal restrictions.
As I recall Wolfsburg west also should have the rubber seal that fits between the tube and the reservoir nipple.
Good luck, teach. Bill.
Last edited by rockerarm on Sat Dec 31, 2016 5:43 am; edited 1 time in total |
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kreemoweet
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Joined: March 13, 2008
Posts: 3898
Location: Seattle, WA
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| Posted: Fri Dec 30, 2016 6:13 pm Post subject: Re: Replacing servo and master cylinder |
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Wolfsburg West seems to be a little confused on this issue. Power brakes (i.e. with servo) were stock on all
71-79 US import busses, as far as I can tell. All those used the same master cylinder, and that cylinder
has reservoir ports spaced at 85 mm. The reservoir itself varied during those years. The '71 reservoir has
the inlet on the left side, pointing rearward. The nylon feed tube from the upper reservoir has about "zero" slack in it,
and very little flexibility, so a reservoir with any other configuration is simply not going to work. I can't really tell from the WW photo of what
they call a 73-79 reservoir exactly where the inlet is, but it looks to me like it will not work with a stock '71 setup.
Not too long ago, I got a new, Genuine VW '71 bus lower reservoir from busdepot.com, and it fit perfectly. It was part #211 611 313J, and was
a very reasonable $19.95.
WW's claim that a power bleeder is needed is complete and utter nonsense. Literally MILLIONS of bus m/c and brake systems have been bled
successfully with no such thing. Anyone taking up such work on thier bus needs to get a decent service manual (e.g. from Bentley Publishers) and
follow the instructions therein.
Here's my review of the 71-72 brake servo I got from WW a few years ago: http://www.thesamba.com/vw/forum/viewtopic.php?t=583610&highlight=
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old DKP driver
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Joined: March 30, 2005
Posts: 4145
Location: Los Gatos,Ca.
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| Posted: Sat Dec 31, 2016 12:03 am Post subject: Re: Replacing servo and master cylinder |
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Times 2 with kreemoweet.
NO REASON FOR A PRESSURE Bleeder.......And,yes that 211 611 313J will fit.
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DougB
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Joined: January 09, 2007
Posts: 1076
Location: Falls Church, Virginia, USA
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| Posted: Sat Dec 31, 2016 9:29 am Post subject: Re: Replacing servo and master cylinder |
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Just beware with the WW servo - their dust boots are kinda crappy...the one on my brand new WW servo cracked and broke after only 2 years. Currently investigating alternatives or may try to design and print my own from rubber filament.
- Doug
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BayCreamPuff
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Location: Oakland, CA
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kreemoweet
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Joined: March 13, 2008
Posts: 3898
Location: Seattle, WA
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| Posted: Sat Dec 31, 2016 2:38 pm Post subject: Re: Replacing servo and master cylinder |
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I see CIP1 is spouting exactly the same nonsense about requiring a 73-79 reservoir. And claim the "J" part
number for it, but another Cip1 website page lists the "J" as being a 71-72 bus part.
Anyway, the VW part number cast into the reservoir that fits my stock '71 setup (and is DIFFERENT from later bay
bus reservoirs) is 211 611 313 5.
I found a thesamba.com thread discussing this same confusion: http://www.thesamba.com/vw/forum/viewtopic.php?t=346964
Seems our VW parts vendors are simply not up to doing their jobs. Pity.
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AhnwS71
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Joined: January 31, 2018
Posts: 215
Location: Huntsville, AL
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| Posted: Fri Feb 14, 2020 9:50 am Post subject: Re: Replacing servo and master cylinder |
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I was trying to get my original MC rebuilt but the fellow said that he cannot locate a part needed. All the parts available are for the new MCs and not the original stock.
He also says that he can get me a new IAP German master cylinder to replace it instead. He says it costs around $60.
I am curious of the quality of the IAP MC when all other new "German" MCs cost closer to $200.
Anyone with any input on IAP MCs?
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kreemoweet
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Joined: March 13, 2008
Posts: 3898
Location: Seattle, WA
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| Posted: Fri Feb 14, 2020 12:45 pm Post subject: Re: Replacing servo and master cylinder |
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There are new "ATE" made-in-China master cylinders being sold for about that price.
That's probably what the IAP part is.
Some parts vendors seem to think it's OK to say a part is "German" if it has an old
brand name from a company that actually used to be German, or if the Mfg. company
has an office in Germany. Just more fraudulent crap.
Even a real ATE "German" master cylinder is likely to be made in Czechoslavokia or some
other E.U. country.
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AhnwS71
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raygreenwood
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Joined: November 24, 2008
Posts: 21512
Location: Oklahoma City
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| Posted: Fri Feb 14, 2020 4:39 pm Post subject: Re: Replacing servo and master cylinder |
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| AhnwS71 wrote: |
I was trying to get my original MC rebuilt but the fellow said that he cannot locate a part needed. All the parts available are for the new MCs and not the original stock.
He also says that he can get me a new IAP German master cylinder to replace it instead. He says it costs around $60.
I am curious of the quality of the IAP MC when all other new "German" MCs cost closer to $200.
Anyone with any input on IAP MCs? |
What "part" could he need that he can't get? You can get complete kits for $33 from Rockauto for a 1971.
Even if old to late are different....its usually only the pistons in a kit. The seals and valves can usually be put onto the old pistons. The pistons never wear out unless they are corroded. Ray |
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kreemoweet
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Joined: March 13, 2008
Posts: 3898
Location: Seattle, WA
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| Posted: Fri Feb 14, 2020 5:22 pm Post subject: Re: Replacing servo and master cylinder |
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| AhnwS71 wrote: |
| a couple of the links above claim to be German and want close to $200. are you saying the quality for them it not worth it anymore? |
I couldn't say about those "German" m/c's. The BusDepot unit looks like the Chinese ATE m/c I have. To their credit, BusDepot
does not claim it to be "German". I haven't installed/used the one I have, so can't say much about quality. The extra port with plug
is a rather nice feature, so you can put your brake light switch where it won't interfere with the parking brake cable, like it would
unless you have the original stock right-angle plug&boot to use with it.
The other m/c's are not built exactly like the original ATE m/c's either, but more like the Brazilian TRW parts, which I haven't
heard many complaints about. They might be more prone to leaking brake fluid into the booster, since they don't have the
original drain/vent passage.
In all cases, the stuff about using a 73-79 reservoir and using a power bleeder is bunk.
You would also do well to disassemble any new m/c you get and clean it thoroughly before installing, even the "German" ones.
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AhnwS71
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Joined: January 31, 2018
Posts: 215
Location: Huntsville, AL
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| Posted: Sat Feb 15, 2020 9:33 am Post subject: Re: Replacing servo and master cylinder |
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| raygreenwood wrote: |
What "part" could he need that he can't get? You can get complete kits for $33 from Rockauto for a 1971.
Even if old to late are different....its usually only the pistons in a kit. The seals and valves can usually be put onto the old pistons. The pistons never wear out unless they are corroded. Ray |
He said there was a seal that was bad and was leaking into the booster. He could not find the exact size seal he needed.
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Sometimes you eat the bar, and sometimes the bar eats you. the Stranger |
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raygreenwood
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Joined: November 24, 2008
Posts: 21512
Location: Oklahoma City
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| Posted: Sat Feb 15, 2020 3:15 pm Post subject: Re: Replacing servo and master cylinder |
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| AhnwS71 wrote: |
| raygreenwood wrote: |
What "part" could he need that he can't get? You can get complete kits for $33 from Rockauto for a 1971.
Even if old to late are different....its usually only the pistons in a kit. The seals and valves can usually be put onto the old pistons. The pistons never wear out unless they are corroded. Ray |
He said there was a seal that was bad and was leaking into the booster. He could not find the exact size seal he needed. |
Yep...outer shaft seal. And...most likely it was not the seal that was bad. About 90% of master cylinders that are being rebuilt (of this age)....will leak at this seal even when the seal is perfect....for three reasons (two actually...but two and an extra reason):
1. The outer seal keeps itself lubricated by leaving a very fine...maybe a micron thick...film....of brake fluid on the wall of the cylinder in the surface pores as it slides in and out.
That fine amount of brake fluid...over time as the outer boot fails with age....absorbs moisture. Sooner or later it is a corrosive paste.
This is why virtually all old master cylinders that are leaking past the outer seal... when taken apart.... have rust and rust pits in the "parking" spot for this outer seal.
The cups when flexible can seal small pits about .001" to .002" deep at the most.....IF THE CYLINDER IS NOT ALREADY OVERSIZED.
2. That last problem....is usually made worse by whomever rebuilds the master cylinder. They see the light rust pits and then....they stupidly (unknowingly would be a better word) run a hone through the bore to get rid of them.
Brake MASTER cylinder bores are NOT honed from the factory. They are LAPPED.
This does not mean that a master cylinder bore cannot be honed.....but it should be MEASURED FIRST...to see if it can even survive honing or lapping (more on this in a minute)....and then honed with a 600-800 grit hone or lapped with about a 1000 grit lap tool. Nothing more coarse than that.
Factory new master cylinders...good ones....do not have hone marks...but they do have a very, very slight texture/tooth from the lapping tool.
You need only a very fine tooth to hold that small amount of brake fluid for cup lubrication. That fine tooth....is 600 grit or above. Anything below that...just tears up the molded rubber cup edges. These are not piston rings that need to be worn in...they are SEALS.
The reason you need lapping or honing with a very fine grit is two-fold.....
A. to leave the fine tooth and not destroy the cups as mentioned above...and...
B. To not inadvertently oversize the bore.....which is NOT just the fault of the person doing the honing or lapping.
Reason 3. This is why I said the bore needs to be measured. The absolute maximum tolerance the master cylinder bore can be....larger than the piston heads of the pistons where they support the EPDM rubber cups....is .005".
Even .005"...can lead to leakage from an NOS cup set that is slightly stiff with age. But from a fresh cup....it should seal...but you might only get 50k miles from it.
So...for example (i'm using my 19mm master cylinder for the example).....if you see the rust pits around the outer seal parking area that I mentioned above....and they are impossible to measure accurately ....what you want to do...is clean up the old pistons or if using new pistons...either way.... ...measure the piston heads where the flat parts of the seals rest.
Lets say they measure exactly 19mm which = 0.7480"
Then measure the bore....before honing to get rid of the pits.
Lets say it measures exactly 0.7510".....which is very common.
This means that the bore is .003" larger than the piston.
I will have to look it up but I believe the tolerance range is .002" to .005"
So most master cylinders...about 7 out of 10.... I find are actually...from the factory...range from .003" to .0045"....  ...yes...when new...they are just fine...still in the tolerance range...but so close to the limit that they cannot be rebuilt....IF...the bore has to be lapped or honed.
So....when you start honing/lapping the bore....you do just a little...then measure it....and inspect the pits. Lets say you increased the bore diameter by .0005"....and the pits disappeared or decreased their span/diameter by about half. But you are now at .0035" on the bore....
You CAN lap/hone a little more...and measure again. Lets say you have now increased the bore by a full .001". You are now at the 75% mark in the tolerance range....at .004"
If the rust pits have reduced to about 2/3 their original width/diameter....its probably safe to lapping/honing stop now...and the outer cup "may" seal just fine. They can usually seal narrow pits of about .001" to .002" deep.
But....too many lap until the pits are gone. Usually the bore is now oversized.... at .005" or over...and the outer cup will never "reliably" seal and the inner cups will bypass under load....because they swell into the gap and change the angle of the lip to the bore.
And all of that hone/stop/measure/hone/stop/measure......that was done decades ago by a dedicated brake shop....never gets done these days. Too much labor cost. Its easier to throw in a Brazilian or Chinese cylinder and send you off.
In the long run...if you have a good German cylinder....if you can do a simple tear down and clean of the outer area and maybe even a reseal kit (keep the original pistons)...every 3-5 years....the master cylinder will never "wear" out. Neither will the pistons.
The pistons do not touch the bores. The pistons ride on the cups. The bores never wear. The pistons never wear. The only thing that kills master cylinders is rust or grit.
So if you keep it bled every other year, no rust in teh system. If you strip it down every 3-5 years....and clean away the water/brake fluid goo from the outer end and never let the rust start.....the cylinder will last forever.
Sorry for the length. Ray |
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AhnwS71
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Joined: January 31, 2018
Posts: 215
Location: Huntsville, AL
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| Posted: Fri Feb 21, 2020 11:44 am Post subject: Re: Replacing servo and master cylinder |
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| kreemoweet wrote: |
You would also do well to disassemble any new m/c you get and clean it thoroughly before installing, even the "German" ones. |
how do you mean clean it? Also, can i disassemble it and put it back together easily? Do i need to have some sort of compression check on it after it is reassembled?
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Sometimes you eat the bar, and sometimes the bar eats you. the Stranger |
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AhnwS71
Samba Member
Joined: January 31, 2018
Posts: 215
Location: Huntsville, AL
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| Posted: Fri Feb 21, 2020 11:50 am Post subject: Re: Replacing servo and master cylinder |
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| raygreenwood wrote: |
Yep...outer shaft seal. And...most likely it was not the seal that was bad. About 90% of master cylinders that are being rebuilt (of this age)....will leak at this seal even when the seal is perfect....for three reasons (two actually...but two and an extra reason):
Ray |
that is the one. He cleaned the MC to look like new and did not charge me anything. he sent it back in pieces. I am pretty sure he did not try to bore/lap it otherwise he would have charged me something. He said that there were NO marking on the cylinder to let him that it is the stock cylinder and could not get the proper seal.
I guess i am in the market for a new MC.
thanks for the explanation Ray. strong work as usual.
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raygreenwood
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Joined: November 24, 2008
Posts: 21512
Location: Oklahoma City
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| Posted: Fri Feb 21, 2020 1:42 pm Post subject: Re: Replacing servo and master cylinder |
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| AhnwS71 wrote: |
| raygreenwood wrote: |
Yep...outer shaft seal. And...most likely it was not the seal that was bad. About 90% of master cylinders that are being rebuilt (of this age)....will leak at this seal even when the seal is perfect....for three reasons (two actually...but two and an extra reason):
Ray |
that is the one. He cleaned the MC to look like new and did not charge me anything. he sent it back in pieces. I am pretty sure he did not try to bore/lap it otherwise he would have charged me something. He said that there were NO marking on the cylinder to let him that it is the stock cylinder and could not get the proper seal.
I guess i am in the market for a new MC.
thanks for the explanation Ray. strong work as usual. |
Its interesting.....ask your guy if he has a source for individual seals please!
See...that outer seal...is a compound seal. Its called a "shaft seal" in some areas. Its cup/lip is just like the other normal "u-cup" seals in the master cylinder....EXCEPT....that it has a "cuff" on the inside of the seal and a rubber base flap. Its designed...to not let fluid leak out on the ID of seal.
If you dig through this thread....you can see the difference in the very outer piston seal.
The inner seals are simple "U" cross section cups. The outer seal has an extra sealing collar
https://www.thesamba.com/vw/forum/viewtopic.php?t=679160
If your builder is buying "U" cups from a source....I would be interested in knowing from who or if I could buy some from him. I am about to start rebuilding some type 4 master cylinders and need a source other than buying kits for type 1 and 3 and throwing the pistons in the trash to rob seals from.
And...I can find plenty of rubber seal shops that can manufacture on their CNC lathes or send from stock....the simpler u-cups for the internal pistons...that are serviceable and of the right material....but none of them can do the outer seal on their CNC rubber lathes. Its a molded part only.
Ray |
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