[T3] Brake Hints!

[Jim Adney]

On 30 Aug 2022 at 10:26, William Jahn wrote:

> How does the brake fluid change process using DOT 3 or 4 differ?

No change.

> I'm not using DOT 5. I've never done one person bleeding before it was always
> a second person pumping the pedal and me working the bleeders. 

For some reason, slow pumping with 2 people is the way everyone gets 
taught to do it. It works, but it takes 2 people and a lot of time. People seem 
to think that there's a big advantage to not drawing in air on the upstroke, but 
once you watch while someone is pumping, you realize that air redraw is a 
non-issue.

> I've watched many videos showing this procedure and granted they are now
> VW specific other than one for Mercedes which was light pumps gravity
> bleed.

ATe (Alfred Teves) made most of the brake components for both VW and 
M-B, as well as many other Euro makes. None of them require or benefit 
from different techniques.

> I understand how the rapid pump churns up old fluid and crud. I've just
> never seen anyone do it or mention it. 

My opinion: Most writeups we come across were done by people who never 
did any of this work themselves. They are writers, not mechanics. They have 
just read other books and are repeating the methods they have read in other 
places, using their own words, of course. Most mechanics get taught the 
same method you're familiar with. Few question it or try anything different.

One caveat: When the hydraulics are empty, it's possible to run the pistons 
in the master cylinder into the end of their travel. If you do this hard, it may 
be possible to damage something. I recommend a few cautious strokes first, 
to find the end of travel and avoid it thereafter.

Once one circuit on a tandem system is bled, there will be a new, reduced, 
end of travel. At that point, you'll need to find the new limit and further 
restrict the later strokes.

Once all the flushing is done, you can return to a slow stroke or just gravity 
bleeding to get any remaining air out.

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