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chaosisme
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PostPosted: Thu Jul 06, 2017 9:18 pm    Post subject: Master Cylinder Issues Reply with quote

Bought an aftermarket master cylinder for my '70 to replace the leaky original. Installed it and it leaked. Exchanged it for another and finally finished rebuilding the brake system and this one leaks too.

Does anybody know a place that rebuilds master cylinders in Southern California?

Also, what is the correct length for the brake pushrod? Is it possible its too long and pushing into the master too far or something? Or is it just a shitty master?
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Wildthings
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PostPosted: Thu Jul 06, 2017 10:19 pm    Post subject: Re: Master Cylinder Issues Reply with quote

Where is the cylinder leaking?
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Tcash
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PostPosted: Thu Jul 06, 2017 10:34 pm    Post subject: Re: Master Cylinder Issues Reply with quote

http://www.karpspowerbrake.com/

http://brakematerialsandparts.webs.com/brakerebuilding.htm

The brake rod would not cause the master cyl to leak.
If it is too long, it would apply the brake slightly all the time. Your drums and rims would be getting hot.

Good luck
Tcash
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chaosisme
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PostPosted: Fri Jul 07, 2017 10:12 am    Post subject: Re: Master Cylinder Issues Reply with quote

Wildthings wrote:
Where is the cylinder leaking?


Out of the front.
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raygreenwood
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PostPosted: Fri Jul 07, 2017 11:16 am    Post subject: Re: Master Cylinder Issues Reply with quote

chaosisme wrote:
Wildthings wrote:
Where is the cylinder leaking?


Out of the front.


How old is it? Meaning....is this a "New Build" master cylinder bought from one of the large VW parts suppliers or is this a rebuild bought through a wholesaler...or is this an "NOS" original cylinder bought on line?

The NOS cylinders are to be avoided except for use as a pristine core for a rebuild using new seals. This is because with age the EPDM seals harden up a little. Its not the hardening process that makes them unable to seal. Its the fact that while they were aging and hardening up they were constrained in the bore of the cylinder which causes the seal lips to maintain the bore shape and they do not easily inflate with pressure.

The most common two issues are leakage at the outer seal and cross pressurization between circuits...which causes improper front to rear balance or weak stopping power.

Just for reference....here is a strip down and refurb with new seals of a top notch NOS ATE cylinder that failed to seal and bleed right out of its pristine box. I have found MANY of these. Its about 60/40 that it will fail right out of the box with these issues or will have a short life.

https://www.thesamba.com/vw/forum/viewtopic.php?t=679160

The other issue with rebuilt master cylinders from large "reman" suppliers...is that after 40+ years now....the pool of original cores that these reman houses have to work with....are beyond the pale. They have either been rebuilt too many times or have enough rust in the bore that they must be bored too far oversized to actually work properly.

The factory spec for bore size versus piston size...and there is some tolerance in both....is .004" oversized maximum before the seals are at risk of not sealing.

So...for example on a 19mm master cylinder like mine the stock size is 19.05mm which is exactly 0.75". The maximum bore oversize compared to piston diameter is 19.1516mm or 0.754".

On a 23.8mm bore which 0.937"...the maximum bore oversize to piston is 23.90mm or 0.941".

In reality its about piston head diameter to bore diameter gap. The pistons are undersized to the bore. They should not touch the bore walls when the seals are installed.

Typically in really good quality master cylinders the bore may be exact to spec within .001" and the piston head is .002" smaller than that. This leaves effectively about .001-.0015" of safe material to remove on re-honing for a rebuild. However I have seen many factory new brake masters over the years with slightly undersized piston heads or slightly oversized bore or a combination of both...leaving the difference right at .003" to .0035"....which is perfectly functional but rarely rebuildable.

Ray
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chaosisme
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PostPosted: Fri Jul 07, 2017 12:24 pm    Post subject: Re: Master Cylinder Issues Reply with quote

raygreenwood wrote:
chaosisme wrote:
Wildthings wrote:
Where is the cylinder leaking?


Out of the front.


How old is it? Meaning....is this a "New Build" master cylinder bought from one of the large VW parts suppliers or is this a rebuild bought through a wholesaler...or is this an "NOS" original cylinder bought on line?

The NOS cylinders are to be avoided except for use as a pristine core for a rebuild using new seals. This is because with age the EPDM seals harden up a little. Its not the hardening process that makes them unable to seal. Its the fact that while they were aging and hardening up they were constrained in the bore of the cylinder which causes the seal lips to maintain the bore shape and they do not easily inflate with pressure.

The most common two issues are leakage at the outer seal and cross pressurization between circuits...which causes improper front to rear balance or weak stopping power.

Just for reference....here is a strip down and refurb with new seals of a top notch NOS ATE cylinder that failed to seal and bleed right out of its pristine box. I have found MANY of these. Its about 60/40 that it will fail right out of the box with these issues or will have a short life.

https://www.thesamba.com/vw/forum/viewtopic.php?t=679160

The other issue with rebuilt master cylinders from large "reman" suppliers...is that after 40+ years now....the pool of original cores that these reman houses have to work with....are beyond the pale. They have either been rebuilt too many times or have enough rust in the bore that they must be bored too far oversized to actually work properly.

The factory spec for bore size versus piston size...and there is some tolerance in both....is .004" oversized maximum before the seals are at risk of not sealing.

So...for example on a 19mm master cylinder like mine the stock size is 19.05mm which is exactly 0.75". The maximum bore oversize compared to piston diameter is 19.1516mm or 0.754".

On a 23.8mm bore which 0.937"...the maximum bore oversize to piston is 23.90mm or 0.941".

In reality its about piston head diameter to bore diameter gap. The pistons are undersized to the bore. They should not touch the bore walls when the seals are installed.

Typically in really good quality master cylinders the bore may be exact to spec within .001" and the piston head is .002" smaller than that. This leaves effectively about .001-.0015" of safe material to remove on re-honing for a rebuild. However I have seen many factory new brake masters over the years with slightly undersized piston heads or slightly oversized bore or a combination of both...leaving the difference right at .003" to .0035"....which is perfectly functional but rarely rebuildable.

Ray


This one is new from IAP. Same as the last leaky one. I was going to try a rebuilt Raybestos but after what you said, I think I might pass.
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raygreenwood
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PostPosted: Fri Jul 07, 2017 1:02 pm    Post subject: Re: Master Cylinder Issues Reply with quote

I would be wary of IAP brake parts....personally. they have had issues.

IAP is part of Dura International or was.....this is old but it says something

http://abcnews.go.com/Blotter/story?id=8051065

From what I have seen....and this is nust my experience...most IAP hydraulics I have seen for classic air cooled cars...and I have only seen maybe 8 MC's.....were all either FAG or ATE castings....which means they are remanufactured.

Outside of brand new new build (not NOS).....in the box ATE and FAG MC's.....I do not trust remans anymore.
On the other hand....most of the Centric master cylinders and calipers are based on brand new centric castings and the quality has been excellent. Ray
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chaosisme
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PostPosted: Fri Jul 07, 2017 4:03 pm    Post subject: Re: Master Cylinder Issues Reply with quote

raygreenwood wrote:
I would be wary of IAP brake parts....personally. they have had issues.

IAP is part of Dura International or was.....this is old but it says something

http://abcnews.go.com/Blotter/story?id=8051065

From what I have seen....and this is nust my experience...most IAP hydraulics I have seen for classic air cooled cars...and I have only seen maybe 8 MC's.....were all either FAG or ATE castings....which means they are remanufactured.

Outside of brand new new build (not NOS).....in the box ATE and FAG MC's.....I do not trust remans anymore.
On the other hand....most of the Centric master cylinders and calipers are based on brand new centric castings and the quality has been excellent. Ray


I saw that Centric offers a new MC but it's 200, I figured for that price I might as well buy a new German one.
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raygreenwood
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PostPosted: Fri Jul 07, 2017 9:13 pm    Post subject: Re: Master Cylinder Issues Reply with quote

chaosisme wrote:
raygreenwood wrote:
I would be wary of IAP brake parts....personally. they have had issues.

IAP is part of Dura International or was.....this is old but it says something

http://abcnews.go.com/Blotter/story?id=8051065

From what I have seen....and this is nust my experience...most IAP hydraulics I have seen for classic air cooled cars...and I have only seen maybe 8 MC's.....were all either FAG or ATE castings....which means they are remanufactured.

Outside of brand new new build (not NOS).....in the box ATE and FAG MC's.....I do not trust remans anymore.
On the other hand....most of the Centric master cylinders and calipers are based on brand new centric castings and the quality has been excellent. Ray


I saw that Centric offers a new MC but it's 200, I figured for that price I might as well buy a new German one.


Great...IF.....you can get an actual "NEW" German master cylinder. Not NOS.....NOT remanned.
Ray
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chaosisme
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PostPosted: Fri Jul 07, 2017 10:57 pm    Post subject: Re: Master Cylinder Issues Reply with quote

raygreenwood wrote:
chaosisme wrote:
raygreenwood wrote:
I would be wary of IAP brake parts....personally. they have had issues.

IAP is part of Dura International or was.....this is old but it says something

http://abcnews.go.com/Blotter/story?id=8051065

From what I have seen....and this is nust my experience...most IAP hydraulics I have seen for classic air cooled cars...and I have only seen maybe 8 MC's.....were all either FAG or ATE castings....which means they are remanufactured.

Outside of brand new new build (not NOS).....in the box ATE and FAG MC's.....I do not trust remans anymore.
On the other hand....most of the Centric master cylinders and calipers are based on brand new centric castings and the quality has been excellent. Ray


I saw that Centric offers a new MC but it's 200, I figured for that price I might as well buy a new German one.


Great...IF.....you can get an actual "NEW" German master cylinder. Not NOS.....NOT remanned.
Ray


Shoot, maybe I might go with the Centric after all. I pulled my old master apart and it doesn't look too bad inside so I might see about getting it rebuilt.
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skills@eurocarsplus
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PostPosted: Sat Jul 08, 2017 6:30 am    Post subject: Re: Master Cylinder Issues Reply with quote

"centric" is rock auto junk....but centric doesn't make parts...they re-box. I rolled the dice on a master for my rabbit. it was cheep, and I knew this going in. it was an ATE that came out of that box.
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PostPosted: Sat Jul 08, 2017 7:24 am    Post subject: Re: Master Cylinder Issues Reply with quote

Check your local NAPA, sometimes their brake stuff is the best out there. Don't always know until you open the box though.
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busman78
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PostPosted: Sat Jul 08, 2017 8:03 am    Post subject: Re: Master Cylinder Issues Reply with quote

So how many "cheap" master cylinders do you want to try? If you like the educational experience of changing the MC, bleeding, frustration, remove, return, try again and repeat many times, plus you already know the cheap aftermarket MC have a high failure rate, the question is when will it fail again. Yep the German MC's are expensive, in the end is it really that expensive to only have to do it once?

I just finished a MC swap in a bug, the owner did not want to spend the $100 for a German MC, instead provided me with a unknown country of origin model, took three of them to get one that did not leak, my labor, fluid and power bleed tool charge are for each install, he provided the part and bought cheap stuff. So the $50 dollars he saved by not buying a German MC has racked up a little over $200 in extra labor charges. Plus this third pump is kinda squishy, I give it a month and will need to be replaced, that will cost him another $100 plus in my labor.

So how expensive is buying quality the first time?
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PostPosted: Sat Jul 08, 2017 8:42 am    Post subject: Re: Master Cylinder Issues Reply with quote

skills@eurocarsplus wrote:
"centric" is rock auto junk....but centric doesn't make parts...they re-box. I rolled the dice on a master for my rabbit. it was cheep, and I knew this going in. it was an ATE that came out of that box.


Centric actually does manufacture parts....just not everything they sell. Yes....they do repackage a lot of items because they do not manufacture a full range of everything they sell. For example....type 3, 4, 914 and some volvo caliper kits sold through places like Rockauto .....have repeatedly been FAG but have been all new manufacture.

They are a fairly large new casting supplier....and I know that for fact because I have done business with Centric as a secondary supppier of certain parts to a much larger 1st tier automotive parts manufacturer who is one of my customers.

I have also installed Centric Calipers and rotorsin 914 and Volvo....that are Centric and are BRAND NEW...not remanned or or reboxed.

The Stop-Tech line of brake parts and a fair portion of the Duralast brake line at Autozone and a fair portion of the Brake best line at O'Reilly for later model cars are also made by Centric .

This is a common practice among ALL automotive parts manufacturers. They all want to offer a full catalog line. However its not cost effective to make tooling for limited run or older vehicles for every part so they source from company to company.

Yes.....depending on what car its for....you may find brand new Centric build parts in the box....or reboxed parts from other manufacturers.

However....my point was.....in general I have never found NOS or ancient stock parts repackaged as Centric.

By the way.....as another example. Ford's entire dealer network is selling Centric rotors over the counter for older cars that have passed the 10 year manufacturing requirement after the end of model. Especially for mid to light 90s and early 2000s models like Taurus and sable.

The quality has been excellent. Ray

I may get to actually visit this faciloty if the intercompany supply deal with my customer goes through next year.

http://www.centricparts.com/news-media/271-centric...h-facility
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