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  •  » 1967 Power brake pedal issue

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    11/13/2021 2:06 PM  #1

    HAVEaSigAR
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    Registered: 1/24/2015
    Posts: 193

    1967 Power brake pedal issue

    Hello all

    My brother in law just bought 67 with a 302/FMX and the brake pedal (which Im certain is not original) doesnt return all the way, you kinda have to pull it up with your foot. Also, it has developed a hiss which seems to come from the brake pedal. Doesnt hiss when its all the way up or when you press it to the floor, only in-between. 

    I'm assuming we need to replace the booster and master cylinder, but would that also solve the pedal return issue? If not, what else could cause the pedal to not fully disengage and return to the top properly?

    Thanks in advance

     

    11/15/2021 1:57 PM  #2

    mustangermike
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    From: Cleburne
    Registered: 4/13/2017
    Posts: 204

    Re: 1967 Power brake pedal issue

    Sounds like you should at the very least change the booster.  Are you seeing any brake fluid leak out of the master cylinder next to the booster?

    Owner of MustangSteve - 1967 Mustang Coupe 302, 2005 Mustang GT
     

    11/16/2021 6:50 AM  #3

    HAVEaSigAR
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    Re: 1967 Power brake pedal issue

    No brake fluid leaks anywhere, but the pedal did not return properly even before the booster started hissing.

       •Thread Starter
     

    11/16/2021 10:19 AM  #4

    TKOPerformance
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    From: Newark, DE
    Registered: 12/15/2014
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    Re: 1967 Power brake pedal issue

    Is it a factory power brake car?

     

    11/16/2021 7:30 PM  #5

    HAVEaSigAR
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    Re: 1967 Power brake pedal issue

    It is not a factory power brake car

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    11/16/2021 10:05 PM  #6

    50vert
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    From: QLD Australia
    Registered: 4/01/2013
    Posts: 1,422

    Re: 1967 Power brake pedal issue

    Pics of the booster and pedal/pushrod area will help.

    "Those telephone poles were like a picket fence"
     

    11/17/2021 4:19 AM  #7

    TKOPerformance
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    From: Newark, DE
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    Re: 1967 Power brake pedal issue

    Yeah, because its hard to know exactly how it was converted.  In '67 the manual brake and power brake cars used different pedals.  The pedals mounted to different holes in the pedal hanger under the dash.  A manual brake pedal is never going to work right in a power brake application.  The power brake pedal mounts very high up on the pedal hanger.  I'd definitely check out the pedal as part of diagnosing this. 

     

    11/17/2021 6:31 PM  #8

    MS
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    From: Canyon Lake, Texas
    Registered: 1/24/2013
    Posts: 12,253

    Re: 1967 Power brake pedal issue

    The 67 PB pedal should measure 5” center to center from the pivot bolt to the booster actuation pin. The booster shaft should have a curve at the end where it connects to that pin. Hissing is normal to the extent where atmospheric pressure enters the booster upon actuation, but the hissing should stop once pedal is fully applied. Lack of the foam rubber around the.booster input shaft makes the hissing more audible. If it keeps hissing with brake applied, the booster is leaking.
    A stuck master cylinder, or booster, or both can cause the pedal to not return. Also fan be caused by stuck caliper piston, caliper slide brackt, or hoses that are swollen shut internally. Or by the pedal being improperly installed. Check to see if the pedal pivots freely without binding or excessive play.

    Money you enjoy wasting is NOT wasted money... unless your wife finds out.
     

    11/18/2021 5:37 AM  #9

    TKOPerformance
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    From: Newark, DE
    Registered: 12/15/2014
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    Re: 1967 Power brake pedal issue

    Yeah, on that last bit, as I recall, the nut for my pedal pivot is a Nylock.  This allows you to tighten it up enough to remove slop, but keeps it so you don't have to over tighten it and restrict pedal movement.  The manual cars use a different setup where that's not an issue. 

     

    11/18/2021 7:02 AM  #10

    HAVEaSigAR
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    Re: 1967 Power brake pedal issue

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    11/18/2021 7:03 AM  #11

    HAVEaSigAR
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    Re: 1967 Power brake pedal issue

    Hissing must be because that boot is torn, I hope these pictures help, its hard for me to get a clear picture with a cell phone under the dash

       •Thread Starter
     

    11/18/2021 6:16 PM  #12

    TKOPerformance
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    From: Newark, DE
    Registered: 12/15/2014
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    Re: 1967 Power brake pedal issue

    Pedal, purshrod, etc. look correct from the pictures.  I'd say at this point that your booster is probably bad. 

     

    11/18/2021 6:22 PM  #13

    MS
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    From: Canyon Lake, Texas
    Registered: 1/24/2013
    Posts: 12,253

    Re: 1967 Power brake pedal issue

    Definitely not a factory booster. I would look for an original type. Your pedal looks correct. Not original, but correct.

    Alot of the aftermarket pedals were too long at the top and would bind up as they moved. Really bad design.  You have to remove it and grind off the top of the pedal where it is interfering with the top of the pedal support.  Some would not even go together they were such a bad fit.

    The pivot tube at the top pivots on a 3/8” bolt. Around the bolt is a steel tube 3/8” ID x 5/8” OD and a few thousandths longer than the overall dimension of the pedal tube plus two plastic bushing flanges. That way, you tighten the bolt TIGHT and the pedal will still move but is held solidly in position. The factory used a thin wave washer in there as well to take up any looseness. Aftermarket pedals are typically a joke using a nylon tube that obviously will not allow you to tighten the bolt.

    I am betting your non-return issue is caused by the aforementioned interference at the top. At the bety leadt, if you remove the pedal to fix the interference, and it is not the interference causing it, chances are good you will figure it out

    Money you enjoy wasting is NOT wasted money... unless your wife finds out.
     

    11/18/2021 8:34 PM  #14

    50vert
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    From: QLD Australia
    Registered: 4/01/2013
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    Re: 1967 Power brake pedal issue

    I'm not a fan of any of the aftermarket "might fit and work" boosters. I used a Bendix type booster from MS on my 67 till I found an original Midland. They both require a firewall mod, the same as the factory did on a power brake car. There is now an aftermarket copy of the Midland, that is supposedly quite good. If you don't care bout originality, get the Bendix type and firewall mod instructions from MS. Ask him for 4 extra nuts and the tip for mounting it.

    It looks like the torn boot was caused by what ever pushrod setup it's using, holding the boot captive, could'a caused the original binding. Could try cutting the torn section off. But my recommendation is the Bendix.
    Edit: Try Steve's binding suggestion first.

    Last edited by 50vert (11/18/2021 9:15 PM)

    "Those telephone poles were like a picket fence"
     

     

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