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Thread: 67 GT 350 power brake issue...

  1. #1

    67 GT 350 power brake issue...

    Helping a friend of mine work on his 1967 GT 350.

    The car sits for most of the time, he drives it about 1-2 times per month. It has the Kelsey-Hayes-type dual diagonal brake booster/master cylinder set-up. It looks like all of the vacuum hoses, etc... are correctly installed and not damaged.

    When the car is first started, the brakes hardly work, although there is some braking - it is minimal. There is also a "whoosh" type sound from the area of the brake booster. As the car warms-up, the brakes begin to work normally and whoosh sound disappears. Are we seeing a brake bleed issue here, or? Please advise!

    I'm a new member. You guys have a great site.

    Thanks.

  2. #2
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    Re: 67 GT 350 power brake issue...

    Sounds like the vacuum source is weak. Where is the vacuum hose hooked up?

    Greg Z

  3. #3

    Re: 67 GT 350 power brake issue...

    Hi Greg,

    I'm going to check the hose(s) next time I work with the car. I remember checking them and they seemed to be o.k. The booster/master cylinder assembly is not old - less than a year old (rebuilt) by a reputable source I've used on my Mustang.

    Thanks for your help.

    Regards,

    Juan

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    Re: 67 GT 350 power brake issue...

    What's vacuum generated at idle. If it's too low, i.e. below 13-14 inches of mercury you
    may get the problem specified.
    Texas Swede

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    Re: 67 GT 350 power brake issue...

    Sounds to me like a booster diaphram issue. I've owned my 67 GT 350 since 1971. I have had the diaphram replaced 3 times now. Possibly todays fuel additives with old diaphram material.

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    Re: 67 GT 350 power brake issue...

    Quote Originally Posted by 1967GTthree5zero View Post
    Helping a friend of mine work on his 1967 GT 350.

    The car sits for most of the time, he drives it about 1-2 times per month. It has the Kelsey-Hayes-type dual diagonal brake booster/master cylinder set-up. It looks like all of the vacuum hoses, etc... are correctly installed and not damaged.

    When the car is first started, the brakes hardly work, although there is some braking - it is minimal. There is also a "whoosh" type sound from the area of the brake booster. As the car warms-up, the brakes begin to work normally and whoosh sound disappears. Are we seeing a brake bleed issue here, or? Please advise!

    I'm a new member. You guys have a great site.

    Thanks.
    The "woosh " sound is typical of a defective brake booster diaphragm. I am not sure why or how it is sealing up when it warms up but change the booster (I would do master to be on the safe side while you have it off) and you will most likely solve your problem based on the information given. Been there done that.
    Bob Gaines, Shelby collector, Shelby enthusiast, Shelby concours judge

  7. #7

    Re: 67 GT 350 power brake issue...

    The fact that the system works well after it heats up is the most puzzling to me. This is why I decided to get additional opinions!

    I have a bone stock '67 GTA (289 4V, C4) with the same brake system (had it since '75) and when the diaphragm goes - it goes! No working when it heats up - it just goes.

    I've checked the vacuum hoses and the vacuum and both are good. No splits or breaks, and the vacuum level is normal for a 271 hp 289.

    Does anybody have a good rebuilder or source where we can have the unit rebuilt? It's an original Midland unit. My friend says it is about 3-4 years old (since it was last replaced/rebuilt).

    Thanks gentlemen for all of the information and suggestions.

    This a great bulletin board!

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    Re: 67 GT 350 power brake issue...

    Try this guy. I went through 2 before he did mine. Been good now for 4-5 years. http://www.boosterdeweyexchange.com/
    GT350 #3014

  9. #9

    Re: 67 GT 350 power brake issue...

    Okay, had a chance to discuss the issue with my friend. He recalls having the booster rebuilt and he found the receipt. It was rebuilt in April of 2006. The unit was rebuilt by a company in Upland, California (near Los Angeles) called Karps Power Brake Service. It's a Midland unit with the strap. The charge was $110.00 which included the master cylinder being rebuilt and the pedal rod adjusted. The cost included the unit being painted semi-gloss black. That's almost 7 years of service (albeit the car sits for about 80-90% of the time). I'm going to help him yank the sucker out later today, and take it to Karp's next week - they're about 15 miles from my office.

    I'll report the results to you guys.

    Here's a link to their website: http://www.karpspb.com/info.htm

    Thanks for all of the input gents.

    Juan

  10. #10
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    Re: 67 GT 350 power brake issue...

    Karps is a good place. I had them sleeve my 67 GT 350's Master Cylinder and also the rear whell cylinders a few years back.
    Just a reminder: if your booster has the factory tag on it, have them re-install it on the rebuilt unit.

  11. #11

    Re: 67 GT 350 power brake issue...

    Thanks Roddster.

    Would do, except there is no evidence of one on the booster. With the penchant for these units to fail over the past 40+ years, I fear that tag is long gone!

    Thanks to all that have posted regarding this issue. I'll keep you advised as soon as we complete the project.

    Regards,

    Juan

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