In message <950918150806_22545390@mail06.mail.aol.com> writes:
> All very good points, Joe. You can't have much reconstructive surgery done
> for the $160 it cost for a new PDWA assembly.
> I suggest bypassing the PDWA and splitting the circuits only after giving up
> on mine and not having the money to replace it right now. I officially do
> not recommend anyone do this.
>
Interesting thing about dual brakes. the pressure created by the rear piston of
a master cylinder moves the front piston. If there is no PDWA, ie the lines are
completely seperate. you blow the rear master brake's circuit, you have no
brakes. Blow the front circuit, you still have brakes at one end of your car
(different cars tan be plumbed differently).
When you have a PDWA installed you have a piston that moves across the openings
for the lines that is moved by differentials in pressure. You lose pressure in
one side and the piston is pushed across the fliud path of the low pressure
side. If its the rear circuit, it allows pressure to build up upstream of the
PDWA so the front piston can be activated.
The above information is a rewording of what I read in a Land Rover factory
manual descrbing how the Gurling dual brake system works in a early eighties
Land Rover.
When I purchased my '68 MGBGT, the brakes worked and were firm. As is my normal
policy for new used cars, I assume the previous owner never changed fluids and
as time was available I replaced all the fluids in the car. When I went to
bleed the brakes, I discovered both the rear cylinders were dry. I pulled the
rear brakes and examined the cylinders, they never had fluid in them! The
previous owner and I had been driving on front brakes only since the cars rear
brakes were last done (the brake light was broken).
Just before I last did the brakes the car was sitting for a while and the fluid
in the rear circuit drained away through a leak in one of the rear cylinders. I
got in started the car, and the first time I hit the brakes there was nothing
but my properly adjusted mechanical brake to stop me, even though there was
fluid in the front circuit. There was no fluid in the rear master cylinder to
be trapped and activate the front circuit since it drained away while not under
pressure.
Just a couple of non Triumph data points. My TR3 doesn;t have dual brakes.
Do as you wish but I believe in a properly functional PDWA. Unfortunatly, the
seals can go bad over time & the piston can corrode.
TeriAnn Wakeman FOR SALE: 1968 MGBGT. British racing green with
twakeman@apple.com black interior. overdrive. recently
US$ 2500 rebuilt engine & brakes. very minor
surface rust at paint scratches
|