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Thread: Plumbing dual circuit brakes in an 88"

  1. #1
    Join Date
    Jul 2012
    Total Downloaded

    Plumbing dual circuit brakes in an 88"

    Hello from Sherwood.

    Back to working on the brake upgrade for Ratel - basically servo assisted dual circuit 6 cylinder 109" brakes replacing the original 10" non-servo setup. This includes the upgraded pedal tower, servo unit and 109" master cylinder.

    I don't have access to another 88" (or 109" for that matter) with the dual circuit plumbing in situ to check where the plumbing has to go - particularly for those bits that are not part of the original setup on a standard pre-80's 88".

    The workshop manual and parts manual are only of limited help here too - the diagrams are contradictory and there is no mention of which pipes fix where on the PWDA valve. I'm assuming that the valve is fitted with the warning switch terminal facing downward and the large blanking screw to the front.

    This is shown in the following photo which I have inverted:

    PDWA_inverted_valve_words by Neil MacLeod, on Flickr

    I've made that assumption based on the parts manual diagram as follows - in particular the circled part:

    Parts_manual_brakes by Neil MacLeod, on Flickr

    Now, I'm assuming from the parts manual diagram that the pipe from the T piece above the rear diff housing goes to the bottom front aperture and crosses the pipe from the front brakes that is plumbed to the bottom rear aperture. This would fit the 109" master cylinder having the rear pipe at the front and front pipe at the rear cf. 88" other way around.

    Is that right?

    Another question is - what is the fifth threaded outlet at the rear of the PDWA valve for? Neither the parts manual or workshop manual show it being plumbed to anything - is it blanked off? I had originally thought this might be for a second line to one side of the front brakes, but that didn't seem to make sense.

    Anyone know the answers or have an 88" or 109" with the correct dual circuit plumbing that I could either get photos of or take a look at?


    1975 S3 88" - Ratel

  2. #2
    Join Date
    Apr 2008
    Dayboro, Qld
    Total Downloaded
    Hi Neil.

    I just checked the dormobile brakes and the pdwa valve, I'll refer to your upside down diagram

    1/ ???? goes to front left wheel
    2/ Front line from MC goes to front right wheel
    3/ Rear line from MC goes to rear brakes
    4/ Front brake pipe (s) goes to Master Cylinder
    5/ Rear brake pipe goes to Master Cylinder

    The warning switch terminal facing upwards and the large blanking screw to the rear

    Hope this helps

    ps I haven't forgotten about the swivel seals !!
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