[T3] test

[Jim Adney]

On 19 Dec 2010 at 9:47, Russ W wrote:

> When I pulled it off, and took it apart, all the seals were hard as rocks.
> Then I remembered a VW bulletin that I had seen.  Do not use brake 
> hydraulic  parts that are over 2 years old. I you must, install a new 
> soft parts in them.

You've mentioned this before and there's got to be something 
interesting going on here.

For many years, whenever I rebuilt an old MC, I saved all the old 
parts. When I took those parts out they were often worn, you could 
see the worn edges on the sealing lips, but the rubber itself would 
still be soft and pliable.

Years later, I went thru those parts and they were, just as Russ 
said, "As hard as rocks." OTOH, I have rebuild kits that are decades 
old, and the rubber in them is fine. I've never seen a rebuild kit 
with hard rubber in it.

I also have some NOS complete brake assemblies on the shelf. I 
occasionally sell one of them, but I always take them apart first to 
make sure they are servicable. So far, they have all been fine. 
I'm guessing that long exposure to brake fluid, or some other fluid, 
leaches something out of the rubber but replaces it with something 
else which keeps the rubber pliable. It must be that long exposure to 
air afterwards allows that substitute to evaporate or migrate away, 
leaving the rubber hard.

I don't know what's going on here, but I'm tempted to take some old 
hard rubber parts and let them soak, some in DoT-3 and some in DoT-5 
for a couple years to see if that brings them back. Just gotta do it 
in such a way that I can remember what I did when I look at them in a 
few years.

I wonder if the new parts sold thru VW, the ones Russ's memo would 
have been talking about, were treated with the special "VW brake 
cylinder paste" and if this might have been the long term culprit.

OTOH, one of our listees send me a MC to rebuild earlier this year. 
When I took it apart it was filled with a very liberal amount of some 
sort of grey goop that he thought might have been VW brake cylinder 
paste. I cleaned the grey goop out, but those parts were all in 
perfect working condition.

So there's still a mystery here....

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Jim Adney, jadney at vwtype3.org
Madison, Wisconsin, USA
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