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67 GT500 Power Booster help!!!

Discussion in '1965-1970 Shelby Mustang GT350 & GT500' started by FIA-ERA, May 14, 2010.

  1. May 14, 2010 #1
    FIA-ERA

    FIA-ERA Member

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    Hey guy's this is just about to drive me crazy! I just got my booster back from being rebuilt from an expert and it still will not stop! This is the third try at this and I'm just spent on what it could be now. The pedal just doesn't have the stopping power and I can not lock the front tires up at all! I had them repair everything, brand new master, adjust the pushrod, and still not much better. I don't know if it's the vacuum not sufficient or what. HELP!! I will try and re bleed but I'm not thinking this is the problem. Does your cars pedal go down 2" before they even think about a slight pressurel? Too much pedal travel for me.

    I'm about ready to put a parachute or something on the back to slow her down! ANY HELP would be GREAT!!! Thanks, Matt
     
    FIA-ERA, May 14, 2010
    FIA-ERA, May 14, 2010
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  2. May 14, 2010 #2
    Shelby~gt350#3000

    Shelby~gt350#3000 Well-Known Member

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    i would suggest trying a few simple inspections:

    First pump brake pedal several times with engine off. Pedal should start off soft then get rock hard. Soft pedal to hard pedal confirms booster is ok. Next start engine, run engine for a few seconds. Turn engine off. Wait a minute or two, then grab hold of booster check valve and remove from booster. Pop like noise should occur followed by a vaccum hise. If all of the actions that I stated occur then that part of the system is good.

    Next raise front wheels off ground. Start engine. spin the front tire by hand, One side at a time. Have a friend in the car begin to press the brake pedal. Pay attention to the amount of time the wheel begins to slow down. As soon as the pedal is pressed you should hear the pads contacting the rotors.

    It sounds like you have air in the system still. Rotor finish can also have an effect on pedal feel and stopping capabilites. Collapsed brake lines, frozen caliper pistons? the list can go on and on. Try the above suggestions first then we can go to the next test.

    Jim

    (if your unfamiliar with the operations and workings of a brake system contact a licensed professional. the views expressed are simply suggestions)
     
    Shelby~gt350#3000, May 14, 2010
    Shelby~gt350#3000, May 14, 2010
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  3. May 14, 2010 #3
    FIA-ERA

    FIA-ERA Member

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    Thanks for the suggestions Jim. I will go out and try to re bleed manually and see what I get. Does it matter which vacuum port I choose on the booster. I don't believe so but it is connected to the smaller of the two. ?? I have replaced everything on the brakes, completely! I can get the car to stop but it is definitely not a confident builder. What is a 67 Mustang with Power Brakes supposed to feel like anyway? Are they soft? The expert re-builder promised I could slide the tires after this rebuild! I've always had 65/66 with nothing but manual brakes! I'm so close to just gutting the Midland Booster and just running a long push rod straight threw it!

    I have faith but I've got to get this one figured out soon! My patience is draining! The ONLY good thing out of this is I've become very good at swapping the parts out. I'll try your suggestions tomorrow, Thanks Matt.
     
    FIA-ERA, May 14, 2010
    FIA-ERA, May 14, 2010
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  4. May 14, 2010 #4
    Shelby~gt350#3000

    Shelby~gt350#3000 Well-Known Member

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    should be only one check valve on the booster with a large vacuum hose attached.

    My Shelby will lock the tires up in a panic stop. Yours should to.

    jim
     
    Shelby~gt350#3000, May 14, 2010
    Shelby~gt350#3000, May 14, 2010
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  5. May 14, 2010 #5
    roddster

    roddster Well-Known Member

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    After you get past all these booster tests, it very may well be frozen caliper pistons. There was a special tool that will expand inside the pistons so you can get enough grip to remove them. I recall that my 67 needed all eight pistons. That was long ago and I have since replaced the calipers.
     
    roddster, May 14, 2010
    roddster, May 14, 2010
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  6. May 14, 2010 #6
    Texas Swede

    Texas Swede Well-Known Member

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    Have you done a vacuum test at idle? Too low and your brakes
    won't work.
    Texas Swede
     
    Texas Swede, May 14, 2010
    Texas Swede, May 14, 2010
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  7. May 20, 2010 #7
    FIA-ERA

    FIA-ERA Member

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    Thanks for all the replies! I went out there and bleed the brakes, larger vacuum line(3/8"), and adjusted the rear brakes, AND replaced the front brake pads! The front pads were glazed over from all the previous attempts with faulty boosters. The booster seems to be fine and all is working! Took it out for a drive and all on the brakes seems to be fine. Now look at my newest thread! I swear I think this car is just snake bit! Matt
     
    FIA-ERA, May 20, 2010
    FIA-ERA, May 20, 2010
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