[T3] NOS Brake Parts

Jim Adney jadney at vwtype3.org
Thu Jun 27 10:49:22 PDT 2019

Thanks, Soren. Yep, you're famous!  ;-)

But I'm embarrassed that I didn't remember explaining that seal already, or 
the fact that you'd sent it out 3 times. My memory is clearly failing....

Yes, that's a well-used seal. You can even see the mark left by the thin 
brass washer it pushed against. I've got a handful of ones I've saved that 
look just like it, but most of the bad ones I have came from tandem MCs, 
where the seals are rings, not full coverage seals. That's probably because 
most of the MCs people have sent me have been tandems.

I've never had the problem you've seen with early failure, but I wonder if that 
might be because I've been using DoT-5 (Silicone Brake Fluid) in all my 
aircooled VW since 1977. That has removed the need for brake work on all 
of those cars over the past 30+ years. It's really a blessing compared to the 
Castrol LMA DoT-4 that I had been using previously.

The VW "B" (Bremsen/Brake) Workshop Manual says that brake parts 
should be stored in a cool, dry place and never more than 2 years. I've got 
stuff that's more than 40 years old but is still fine. OTOH, if someone buys a 
MC from me, I always open it up to check that everything is still good. So far 
I've never come across a problem.

In brake parts that I've gotten for rebuilding, the most common problem is 
rust on the metal parts with a failed seal coming in close 2nd, but a few times 
I've seen a really odd problem: I have some seals that have turned rock 
hard, but only in places, not all over.

I have some seals that turned rock hard all over; they were used and turned 
hard after sitting in air for a few years. My guess is that the brake fluid they 
had been in had dissolved the plastizers in the rubber, but the rubber had 
been kept soft by some amount of absorbed brake fluid, which leaked out 
over a long exposure to air. That's just a guess, but it's the only explanation I 
have. That's the same problem I see with O-rings in fuel pumps that have 
been allowed to dry out.

BTW, I've NEVER replaced a rear wheel cylinder. It's much easier to clean 
them up right on the car: disassemble, hone, clean the bore, clean the parts, 
lube, reassemble. I don't think I've ever ever needed new parts.

Thanks for responding. I'll try to remember not to bring this up again.  ;-)


On 26 Jun 2019 at 23:53, Soren Jacobsen wrote:

> > On Jun 8, 2019, at 2:20 PM, Jim Adney <jadney at vwtype3.org> wrote:
> > 
> > Quite a few years ago, someone here posted a link to a photo of a seal that 
> > came in an NOS master cylinder rebuild kit that he had just bought. He did 
> > this to point out the folly of buying NOS with the thought that it would still be 
> > good. The seal in this photo was clearly WAY past its due date.
> > 
> > Anyone else remember this? Anyone care to claim that post and photo? If it's 
> > your photo, plese post that link again.
> I'm famous!  http://blef.org/vw/t3/20mmMCrottencup.jpg
> > I was too busy to respond at the time, and, over time, the opportunity slipped 
> > away from me. In case that photo made a lasting impression on some of you, 
> > I've long meant to respond to it.
> Turns out I sent you that photo privately once in 2012 and then to the list in 2013.  The first time you responded to my immediate question but didn't comment on the "dirty rotten NOS rubber seals!" aspect, and the second time you made a comment that you'd only ever had problems with rusty bores, never rotten rubber.
> ...and it turns out that I sent you this picture a THIRD time (I guess I really like passing this picture around! Sorry to have caused you so much angst, Jim!) in 2017.  Your message here sounded real familiar, because the third time, you wrote:
> "My guess is that what you got in that MC is an old, used seal. I occasionally get a kit with one old seal swapped in. This must happen when someone decides to steal the one part they need and then return the kit as defective.  I've never seen that in a complete MC, but it's equally possible. I just never  buy new MCs.
> A few years ago, someone (you?) posted a link to a photo of the parts in an MC kit that they had just purchased, warning us to avoid buying old kits. The ONE seal that always goes bad in our MCs was clearly falling apart, and the poster thought this was due to age. In fact, that seal looked EXACTLY like the ones I often pull out of old MCs. I'm sure it was a used one that had been  swapped into a kit and then returned.
> I have tons of very old kits on my shelves, and they are all just fine, except for the very occasional kits where 1 seal has been stolen and the kit returned to the shelf."
> > BUT, here's the takeaway: I've got a basement full of NOS brake kits, many 
> > 30-50 years old. I've never had a NOS seal that looked like the one in that 
> > photo.
> In the years since 2012, I've since bought a few NOS master cylinder rebuilt kits myself, and indeed, the rubber pieces all look fine.  I've never used any of the pieces, though, they're just sitting in boxes looking pretty.
> > Just wanted to clear this up, at least in my own mind. I kept thinking about 
> > that photo and how unfortunately misleading it was. And I want to make clear 
> > that it's not the fault of the person who posted the photo; he only had a 
> > sample of 1 and made a reasonable conclusion from it.
> The other thing rattling around in my brain at the time was a note VW included in the 1961-1965 type 1 shop manual: "Assembled master and wheel cylinders should not be stored for longer than 1 year.  If a longer period of storage is unavoidable, the parts must be disassembled and examined.  The rubber parts should not be exposed to daylight when stored for prolonged periods."  I seem to also recall Russ mentioning the dealership practice of ensuring that hydraulic brake parts didn't sit around for long on shelves, but I could be misremembering because in
>  a quick search I can't find any comments to that effect.
> In recent years I've had several rear wheel cylinder leaks on three VWs.  New production cylinders in two cases, old ATe cylinders that had been honed and given new NAPA cups in the other case.  These all leaked within 5 years, which is pretty lousy in my opinion.  Then there was the ATe master cylinder I bought new for my Bug.  It failed in 3 years.  Replaced it with some $20 Chinese AC Industries unit, which has been trouble-free for the last 9 years.  I guess at this point I just consider rubber brake pieces to be a gamble ;)  Do your best and then cross your fingers!  (And maybe switch to DoT-5 if you're lazy like me and still haven't taken the plunge.)
> Soren
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Jim Adney, jadney at vwtype3.org
Madison, Wisconsin, USA

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