RE: [T3] Rear Drum Brakes

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

On 28 Jan 2008 at 14:38, Jacob Hoffman wrote:

> I was wondering about that myself.  Having no assistant the other
> night, I bled the brakes with a hose going up from the bleeder valve. 
> (the over-the-tire method, so to speak)  It seems to me that enough
> brake fluid leaks past the threads in the bleeder that air could be
> getting back in that way.  Maybe I can get my wife to pump my pedal... 

The upward looped hose is completely sufficient to prevent the 
backflow of air into the system. What you've done is exactly right 
and completely sufficient.

Over the years, one thing I've noticed about all the writeups I read 
about bleeding brakes is that it's likely that the writers have never 
actually done it. Every book will talk about pumping up the pedal and 
then letting an assistant open the bleed valve and then close it 
again. This has lent a mistique to the process that is unnecessary.

You don't need to open and close the valve if you just connect a tube 
and loop it upwards and then down into a jar of fluid. You really 
won't draw any air backwards, and if you actually do, then that tiny 
bit will get expelled on the beginning of the next downstroke.

Here's are a few hints: 

A tiny amount of air will only have a tiny effect.

You can actually bleed your brakes without pumping at all; you can 
just fill the reservoir and let the fluid pressure due to the height 
of the reservoir above the MC (in hydraulics, this is called "head.") 
push the air out. Pumping will make this go faster, but gravity does 
just as good a job.  

You don't have to do it in any particular order, but doing the longer 
lines first will get the job done faster. I generally go 'round and 
the round car, bleeding each wheel twice.  

You don't have to tighten up any of the brake adjusters to make this 
work. There's only insignificant pressure in the lines when you're 
bleeding, so none of the pistons, other than the MC, move anyway.

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

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