The brake lines from the master cylinder generally go into a metering block
(has the brake warning light switch if the rear and front brake systems
have
a large difference in pressure between them). This block may have valves
that do not flow fluid unless the pressure is a particular positive value.
This prevents vacuum in the lines that could suck in air or water. You
need
full brake pressure to get fluid through here or blow fluid through the
system after this metering block.
The switch below the steering column is to turn off the wiper blades. I
hope I am remembering correctly, but the blades will not operate unless
the
vacuum operated door is open. This prevents major damage if the blades
were
to operate with the door closed. Once the door opens, there is a switch
near the firewall on the engine side that powers the wipers. In case
there
is a vacuum problem, the wipers may not turn off. This is what the under
steering column switch does.
Vito
"George" <georgewbell@[EMAIL PROTECTED]
> wrote in message
news:2d19c529-41f0-4528-b1cb-34adb82b2dbc@[EMAIL PROTECTED]
> About the end of March I asked this group about the brakes on my 1970
> 350 cu in. 350 hp. convertible. The consensus was new callipers.
>
> I got new back callipers and all the parking brake bits and that is
> all OK, but before bleeding the rear and replacing the front, I
> decided to blow out all the old fluid from the master cylinder and the
> pipes. I took off the master cylinder, cleaned and re-sealed it and
> assembled it with new 4 dot fluid.
>
> I tried to blow out the pipe to the rear with the rear callipers
> disconnected, but the pipe seemed blocked. The brakes were working OK
> before. I tried sucking with a vacuum supply, but that did not work
> either. So I filled up the master cylinder reservoirs with new fluid
> and tried to pump it through. Apart from a couple of tiny bubbles
> coming out, the fluid did not seem to be going into the cylinder. The
> brake pedal was not building up pressure. So why is this, I have left
> it for the night and maybe it needs some fluid to seep through to
> allow the pumping action to take place?
>
> Has anyone got any ideas as to why this should be. I also would like
> to know what the small (broken) switch is that sits between the two
> vacuum overrides for the headlights and the wiper flap, under the
> steering column. Where do the vac. pipes from these two vac. taps go
> to in the engine compartment? I need to trace out where I am losing
> the vac to these two circuits.
>
> Thanks for any comments; they will be most welcome, if anyone knows.
>
> Regards George.
>
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