[s-cars] S-CAR-List Digest, Vol 84, Issue 53

[Paul Heneghan]

Sound advice if Greg is taking his car on the track, but he says he is not
tracking it.

German car manufacturers suggest replacing the brake fluid in their cars
every two years. This brake fluid is in a vented container (caps on
reservoirs have a small bleed hole) and is exposed to extremes of
temperature, pressure and humidity. Water moleclues also permeate through
rubber pipes, and the end result after a couple of years is a significant
water content - typically as much as 4%. This can lower the boiling point
from the original 450F to 300F.

How much water gets absorbed into a sealed container of brake fluid? The
plastic bottle is probably pretty impermeable, but unlikely to be totally
impermeable. There will probably be a few molecules of water vapour in the
air at the top of the container. Therefore the water content will increase
very slightly leading to a drop in boiling point of possibly a few degrees.
What about a container that has been opened and then closed again by
screwing the cap on tightly? Obviously an even greater drop in boiling
point, but nowhere near as bad as two-year-old brake fluid that has been in
an abused car.

As you can see, I have no facts and figures, and am operating on a little
bit of science and lots of gut instinct! My method of operation is as
follows:
Brake fluid in a sealed container bought in the last couple of years - OK
Brake fluid in a tightly closed (but previously opened) container bought in
the last couple of years - OK for a road car.
Brake fluid removed from a car - even if only recently added - discard
Brake fluid from a container of unknown history - discard

I tend to buy five litre containers, and get through each (maintaining two
cars) inside two years.

Feel free to disregard all this and only use newly-opened containers, even
on road cars. You will have marginally improved the braking performance of
the car if you need to perform frequent 70 to 0 stops, or descend long hills
without using engine braking.

For road use there are lots of other safety-related matters more deserving
of your attention. Have you replaced your air bag - look at the date on the
sticker on the B pillar. What condition are the rubber brake hoses in? I had
one burst catastrophically last year. How many mm of tread remain before you
replace your tyres. What is the condition of your track arm lower ball joint
and the retaining pinch bolt?

Living dangerously!

Paul



-----Original Message-----
Date: Fri, 22 Oct 2010 09:15:05 -0400
From: Jared Robinson <chapel976 at gmail.com>
Subject: Re: [s-cars] Superblue Brake Fluid Shelf Life
To: Gregory Wolters <gjwarch at sbcglobal.net>
Cc: S-CAR-List <S-CAR-List at audifans.com>
Message-ID:
	<AANLkTineYxpuY6NmMEW4SCkGOotS_qcehXmLvZyinXT0 at mail.gmail.com>
Content-Type: text/plain; charset=ISO-8859-1

it is hygroscopic... but if it still is sealed (and not just capped, but has
the pull seal still intact) it should still be good

If the seal is removed and the product is capped, I wouldn't trust it beyond
a year from opening.

On Mon, Oct 18, 2010 at 3:55 PM, Gregory Wolters
<gjwarch at sbcglobal.net>wrote:

> Hi,
>
> I bought some years ago... still sealed in container.
>
> Does it have a shelf life?
>
> Greg
>
> 94S4
> 95.5S6
> 97 A8
> _______________________________________________
> S-CAR-List mailing list
> http://audifans.com/mailman/listinfo/s-car-list
> http://www.audifans.com/kb/List_information
>



--
Jared Robinson