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  1. #1
    FEP Power Member Broncojunkie's Avatar
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    Default Replace booster for good measure?

    I'm doing pretty much a complete overhaul of the brake system on my 79 cobra. New drums, shoes, hardware, cylinders, pads, calipers, rotors, bearings, and master cylinder. My question is, should I replace the booster too? I don't mind doing the work, but I've never had a booster go bad and I've heard some stories about new and reman boosters being bad right out of the box.

    So what do my fellow 4-eyed experts think?

  2. #2
    FEP Senior Member fascat's Avatar
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    I had the master cylinder go out in my '86 Capri. Hit the brakes and the pedal went to the floor. When I replaced it I also replaced the booster since I think the fluid leaked back into the booster. I'm pretty sure it was a reman booster. Got it all back together and I could hardly push the brake pedal. I had bench bled the master cylinder and bled the brakes so my first thought was the booster. Looked online and a hard pedal was a symptom of a bad booster. I took it to a garage for further diagnosis and it was a bad booster. So you are right, you can get bad boosters out of the box.

  3. #3
    FEP Power Member Broncojunkie's Avatar
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    Default

    I guess the real question is, how likely is it the old one is still good? I guess worst case scenario is I have to replace it later.

  4. #4

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    If the old one is still good I wouldn't replace it. If it is bad I would see if " Booster Dewey" rebuilds Fox boosters and send yours out to be rebuilt. He does the vintage mustang boosters and a lot of people on those forums recommend him. I think my dad had the booster for his Mach1 done by him years ago and had no problems with it, still working today.
    http://www.boosterdeweyexchange.com/
    85 GT - owned since 87

  5. #5

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    Test to see if the booster held vacuum overnight (or after a week) by pressing the brake pedal before you start the engine.
    Should get a couple pushes on the brakes with vacuum assist.

    Sometimes they only leak when the pedal is press.
    Again with the engine off, press the pedal once and hold it down.
    If there is a leak, eventually the pedal will start pushing back on your foot.

  6. #6

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    If a master cylinder leaks fluid past the piston seals, that fluid normally won't enter the brake booster,
    unless the pushrod seal is also defective. Normally the fluid will just run down the outside front face of
    the booster unit That usually ends up lifting paint, but no permanent harm is done.

    We've had some members going through and pre-emtively replacing a lot of parts that weren't bad, and
    usually, it doesn't end up working out as well as they had hoped...
    Last edited by JACook; 11-22-2017 at 04:49 PM.
    Cheers,
    Jeff Cook

    '85 GT Hatch, 5-speed T-Top, Eibachs, Konis, & ARE 5-Spokes ... '85 GT Vert, CFI/AOD, all factory...
    '79 Fairmont StaWag, 5.0, 62K original miles ... '04 Azure Blue 40th Anny Mach 1, 37K original miles...
    2012 F150 S-Crew 4x4 5.0 "Blue Coyote"... 65 coupe, 289 auto, Pony interior ... '67 coupe 6-cyl 4-speed ...
    '68 Vert, Mexican block 307 4-speed... '71 Datsun 510 ...
    And a 1-of-328 Deep Blue Pearl 2003 Marauder 4.6 DOHC, J-Mod, 4.10s and Lidio tune

  7. #7
    FEP Power Member Broncojunkie's Avatar
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    Default

    That's what i figured, JA. I think I'll take my chances and see how it does.

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