Re: [T3] Brake Bleeding

["Jim Adney" <jadney@vwtype3.org>]

On 30 Aug 98, at 13:02, beemerrider@juno.com wrote:

> .>snip<
> >In any case, installation of Dot 5 requires special understanding, 
> >techniques, and skills. 
> 
> Well, the need for special understanding, techniques and skills sounds
> like one  good reason to stick with glycol-based fluids. 

Everything we do on our cars requires special skills to do 
successfully.  The point I needed to make was that you should not 
just install the Silicone fluid assuming that you could just top off 
the system as if you were doing so with a polyglycol fluid.

> Another is that
> there is very good DOT 4 and DOT 5.1 fluid out there that will exceed the
> performance requirements of any of you.
> DOT 5.1 is fluid with the same chemical basis of DOT 3 & 4, but which
> meets the performance requirements of DOT 5.  Sure, it's hygroscopic, but
> this helps keep water from collecting in low points of the system, if the
> fluid is changed periodically.

I have not heard about the DoT 5.1, but I have not been out there 
looking either.  Both 3 and 4 have plenty of performance (high enough 
boiling point) for our cars.  The lubricity and hydrophobic nature of 
the DoT-5 is what gives it its great advantage.  I am a little 
disappointed that there is a DoT-5.1 that is a polyglycol base.  This 
can only lead to confusion.
 
>  I understand that Ford (remarkably enough)
> sells an excellent "heavy duty" DOT 4 brake fluid.

So does Girling (LMA-4) and ATe (Alfred Teves, the manufacturer of 
our brakes.)  Did you know that the OE brake fluid in our cars was 
ATe Blue DoT-4?

> In my experience, when multiple sources warn against something like this,
> there is *some* basis for it.  Until I understand that basis fully, I'm
> reluctant to ignore it.

I have spoken at length with the man at Dow-Corning who ran their 
several year long test program.  While this was done in the 70s, so 
there was no testing on ABS cars, they had no trouble with the fluid 
causing problems in the hundreds of cars they installed their fluid 
in.

He pointed out to me that ATe purchases DoT-5 by the carload to use 
as an assembly fluid so their parts don't rust on the shelf (as they 
will if you use polyglycol fluids.  He didn't know why the Bentley 
manuals warn against using the silicone fluids on the water cooled 
cars, but he did point out that Ate does not sell a silicone fluid, 
while they do sell a DoT-4.  So there may be a bit of conflict of 
interest in the Bentley statement.  [Ate is very tight with all the 
German and European auto manufacturers, so they have some clout with 
VW, who authorized the "Official" service manuals.]  Of course there 
is also some self interest on the part of Dow-Corning, but I feel I 
have done enough of the VW water-cooled cars to know if it was going 
to cause any problems. 

I have not done any ABS cars, and perhaps that is what the DoT-5.1 is 
intended for.

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