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bleeding brakes with prop combo valve that has push pin ?

Discussion in 'The Garage' started by R72K5, Mar 27, 2005.

  1. R72K5

    R72K5 Banned

    Mar 5, 2001
    Likes Received:
    central IL
    on systems with the push pin in the end of the combo valve how do you bleed them correctly ? i need to run both systems out completely to flush all the old wet fluid out with new fluids, new master cylinder is going on soon,

  2. diesel4me

    diesel4me 1 ton status Premium Member

    Jul 24, 2003
    Likes Received:
    dont touch it if you dont have too!

    We almost never had to mess with the proportioning vave pin on 95% of the cars and trucks we bled at my friends repair shop--and usually when we did attempt to move the pin if we had a stubborn vehicle that would not bleed easy onthe first try-,it would stick or snap off,and off to the junkyard for another! :blush: we learned to stay away from the pin and the proportioning valve unless absolutely nessasary.

    If we did a brake system flush,we disconnected the lines at the calipers and wheel cylinders,and then put compressed air into the brake lines that were removed from the master cylinder,and put the air gun to those lines--most of the ones we did that too needed a new line somewhere after "blowing them out"--litterally!! :crazy:
  3. dyeager535

    dyeager535 1 ton status Premium Member

    Dec 13, 2000
    Likes Received:
    Roy WA
    I second the "leave it alone" comment. IIRC, some GM manuals at least, say that the valve should "self center" itself under most brake bleeding operations. The pressure alone should be enough to push the "valve" back where it needs to be.

    Thats exactly what happens when the brake light goes on/off, it means that piece is moving as it is supposed to. If the light never goes off, then there would be a problem.

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