At 08:28 AM 1/24/97 -0800, you wrote:
>I have come across two kinds of Girling dual master cylinders. one type
>has a mechanical connection between the two master cylinder pistons and
>rely on the PDWA as a warning that one of your brake circuits is not
>holding pressure. The other type (The one in my Land Rover) does not have
>a mechanical connection. The front piston relys upon the pressure from the
>rear to push it. Without a PDWA if the circuit on your rear master
>cylinder fail you do not have brakes. This type master cylinder relys upon
>the sliding piston in the PDWA to close off the rear circuit in case of
>failure. There are different kinds of PDWAS and they should be matched
>with the master cylinder.
>
>Make very very sure which type of gurling master cylinder you have before
>even thinking about removing a PDWA. On the other hand if you do, at worst
>you end up with the same level of risk as us TR owners with single master
>cylinders have.
>
>TeriAnn
>
>twakeman@scruznet.com
>
>
Actually, this sounds a lot like the type of master cylinder most
American cars have, which is referred to as a "floating piston"
unit. The pedal is mechanically linked to the piston in the rear
half of the master cylinder, the pressure of which operates on the
front, keeping the systems balanced pressure-wise, although
hydraulically separated. The fail-safe is that if the circuit
operated by the rear half of the cylinder fails, the pedal will
push the rear piston forward until it touches the front piston,
which will then operate the front circuit. Anyway, that's the
way they were when I was working in an auto shop about 15 years
ago . . . Lord only knows what all those little gizmos on the brakes
do these days!
Mark Moburg
markmoburg@mindspring.com
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