Will a residual pressure valve help..
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  1. #1
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    Will a residual pressure valve help..

    My cortina has regular ford m16 calipers at the front and mk3 escort discs at the Rear, has a single circuit 0.7mm master cyl. Ive bled it many times and am certain there's no air. Still I have a poor pedal and little stopping power. If I clamp off the rears I get a good pedal and pretty good(front only) brakes.
    I can't understand what's happening, would fitting a proportioning valve or a 2lb residual pressure valve help or do I need a bigger master?
    Thanks
    Ian

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    Official RnS Addict 296moon's Avatar
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    have a look here, might help you, https://www.rodsnsods.co.uk/forum/top...ylinder-414009

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    Gym Junkie chrisvs's Avatar
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    Think you've got your MC bore size wrong, maybe 0.7 in
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  6. #4
    I'm a grown up drunk! chevy2's Avatar
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    If you've got poor stopping power now with a 0.7" master, by going to a larger bore one will only give you a higher pedal and with even less stopping power than you have now,
    you probably have an issue with your current setup to deal with,
    you may still have air in there,
    a residual valve is only needed to retain a small amount fluid pressue in the system without drain back to the master if the master is lower than the calipers or wheel cylinders, ie with an underfloor master cylinder.

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    That's what I figured too, it's just that I've tried everything I can think of, have bled it countless times and there's no air. I've established the problem is at the back as I can remove the problem by clamping the hose off

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    I'm a grown up drunk! chevy2's Avatar
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    Not necessarily,
    clamp off the fronts and run through it and see if you get a similar pedal to when the rear system is clamped,
    its gonna be a better/higher pedal as you're now only feeding two calipers.

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    The rear calipers are going to displace a lot more fluid than the old drums, so you are going to need a longer stroke M/C, not a bigger bore, that would just make for a harder pedal. I'm pretty sure that's how I did it on my old Anglia (it was along time ago )

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    Are you sure the pushrod is long enough and displacing enough fluid when pressing the pedal?.

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    Quote Originally Posted by chevy2 View Post
    Not necessarily,
    clamp off the fronts and run through it and see if you get a similar pedal to when the rear system is clamped,
    its gonna be a better/higher pedal as you're now only feeding two calipers.
    Yes, I clamped both fronts off and got a reasonable pedal, not as good as just fronts. Feels like there's a little air in the rears but I really have done everything and can't get any more air out!

  12. #10
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    Quote Originally Posted by Frankee View Post
    Are you sure the pushrod is long enough and displacing enough fluid when pressing the pedal?.
    The pedal doesn't go completely to the floor although it is very close. A longer pushrod will raise the pedal I suppose but I think brakes will still be poor

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