Date: Sat, 19 Feb 2000 10:37:37 -0600
Reply-To: John Rodgers <inua@HIWAAY.NET>
Sender: Vanagon Mailing List <vanagon@gerry.vanagon.com>
From: John Rodgers <inua@HIWAAY.NET>
Subject: Re: Hydraulic System Bleeding
Content-Type: text/plain; charset=us-ascii
From my own experience as an aircraft mechanic and owner of several small
airplanes....pressure bleeding is the way to go.
On many small aircraft and large ones as well - (there are exceptions -
airliners have hydraulicly boosted pressure systems for extra braking power
....whole 'nother story)- there are separate master cylinders....one for each
brake - right and left - located under the rudder pedals on the floor. For right
braking action the pilot depresses the top of the rudder pedal, and similarly
for left braking action. The master under each pedal has a vent plug that vents
the cylinder. That plug can be unscrewed and the hole used as a filler point.
That method however tends to introduce air bubbles into the system.
The most common pressure bleeding method is by use of a hand oiler with a hand
operated pressure pump as part of the oiler. A piece of clear tubing is attached
to the oiler spout, and the other end is put over the bleeder port on the brake
and the oiler handle is operated. This pressure forces the hydraulic brake fluid
up through the system where it is finally forced out of the vent at the top of
the master cylinder. This up hill pumping purges all air out of the system.
This principle can be applied to the servicing of the vanagon hydraulic clutch
and brake actuating system, and eliminate a lot of headaches with entrapped air.
My $.02.
John Rodgers
88GL Driver
McComas_Glenn wrote:
> Just when you all thought this bleeding thread had died..........
>
> In the aviation industry, they use pressure bleeders that fill from the
> slave cylinder end; also have a connection at the master cylinder end for
> handling overflow from the reservoir. This information comes from a skilled
> friend who is a commercial-airline pilot, able craftsman, old airplane
> restorer..... all 'round good guy. He says the hydraulic systems of
> aircraft need to be very tight and bubble-free, and bleeding from the slave
> end is preferred practice.
>
> This idea might not work as well on autos, where the wheel cylinders seem to
> accumulate most of the rust and dirt...... but it would be easy to fabricate
> this kind of pressure bleeder. For someone who keeps his/her hydraulic
> system clean, it may be an opportunity? Any thoughts? (Jason: your
> father may have ideas on this.)
>
> Enjoy Saturday ----
> Glenn McComas, Queenstown, MD
> 87 Vanagon rod knock; 69 Baywindow leaky sunroof; 87 vdp XJ6 scored rear
> disks....
| 
