I get how they are supposed to work.  The problems I've seen and heard of
come when they do get dirt into the ball valve seat or a spring fails.  The
bleed-quality is depending on those little  balls and springs being able to
give a  perfect seal between each stroke of the pedal..
   You push down, fluid is forced out, then the ball valve is supposed to
close while the pedal goes back up..."Supposed to" being the key words.
Dirt sometimes is in the way. If it doesn't close 100% each and every time
on every stroke for each wheel over the life of the speed bleeder, you get
air into the fluid.  It sucks! (pun)
 If you open the valve during a normal bleed, you are supposed to close it
before you release the pedal.  With a Power bleeder in place, you have
"outward" flow from the time you open the bleed screw until you close it.
Unless you have a tiny Salmon-dirt that can swim upstream, dirt can't go
against that positive outward flow..
  Maybe I am just anal, but I am loath to add complexity to a system like
brakes without any real reason. The Power Bleeder systems do what the speed
bleeders say they do..make bleeding hydraulics a one man job.  The Speed
bleeders have been known to NOT... Who knows who made that particular set of
springs and balls in the speed bleeders you will be depending on to stop
your van..
   During my racing "career", I saw a few races lost because of those
things...Never saw any dead guys as a result of speed bleeders, but I did
see some pretty pissed-off drivers who thought they should have good brakes
and ended up not..
  Don Hanson

----- Original Message -----
From: "Mike S" <mikes@flatsurface.com>
To: "Don Hanson" <dhanson@GORGE.NET>
Cc: <vanagon@GERRY.VANAGON.COM>
Sent: Wednesday, June 11, 2008 4:53 PM
Subject: Re: Speed bleeders? Not me

> At 07:02 PM 6/11/2008, Don Hanson wrote...
> >   Personally, I wouldn't use speed bleeders.  Just one more possible
> > failure
> >point...   Which one might be leaking air..?  And now, is that pesky
> >piece of grit that held open the ball valve of the speed bleeder gone?
>
> You apparently don't understand how they work. When you screw them
> closed, they seal exactly the same as a standard bleeder screw, the
> ball valve only comes into play when they're open. If you have a
> problem because dirt is interfering with the ball valve, you would have
> even more serious problems with the same dirt which would have been
> sucked into your brake cylinder when using a normal bleeder screw. Just
> use the dust caps (why are those things so darn expensive???).
>
> Having said that, I agree that investing in a pressure bleeder like the
> popular Motive, makes more sense in the long run. It will also help
> with more modern cars, where you might need pressure to bleed an ABS or
> clutch. For the price of 2 cars worth of Speed Bleeders, you can have a
> pressure bleeder.
>