Brake question

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Feb 5, 2006 | 02:16 PM

mouse777

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Joined: May 2004

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From: WA

Brake question

71 f-100, added a vacuum booster from a mid 70's F250. Used a rebuilt 73 drum/ drum master cyl.{truck is drum/drum]. The booster has a link in the bracket to the firewall which raises the boost up to clear the air filter housing [302 sefi from 87 Victoria]. The flat bar from the boost connects nicely to the pedal. Problem is, the pedal goes down 3inches to apply brakes. Brakes are bled well, pedal does not pump up with pumping. Braking is solid with the after the 3inch travel. I would like less free travel. Before upgrade travel was 1inch. Pedal ratio is about 5 to 1. Any idea's ?? Thanks ahead of time.

Feb 5, 2006 | 08:23 PM

Ford_Six

Hotshot

Joined: Oct 2002

Posts: 18,488

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From: The Big, Oregon

Make sure all your hoses are free of cracks, and can't expand at all when you hit the brakes. Also, double check the right front, these trucks like to hold air there due to the line routing.

Feb 7, 2006 | 01:41 PM

1975Ford

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Did you bench bleed on vice, all of the air out of the master cylinder? rebleed wheel cylinders after.
Try readjusting the front and rear drums.

Feb 7, 2006 | 03:31 PM

charles jones

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Joined: Mar 2005

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From: Mesquite, Texas

It sounds like the rod from the back of the master cyclinder to the front of the booster is to short. If it is an adjustable one let it out and see if the travel differnce is shortened. If its not adjustable use a longer rod and try it. I think 1/4" rod length equals about 1" pedal distance

Feb 7, 2006 | 03:50 PM

stuart1

Cargo Master

Joined: Jun 2003

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From: Somewhere Saskatchewan

Here is a place to start.

Feb 7, 2006 | 03:53 PM

1975Ford

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Here is another link showing the rod and the adjusting nut at the end, its for a F250 like yours, https://www.ford-trucks.com/user_gal...=94721&width=0

Feb 7, 2006 | 04:09 PM

mouse777

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Joined: May 2004

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From: WA

Thanks guys. Master bench bled well, brakes bled well, hoses good. Next was to pull master and check travel from boost, but the image from 1975Ford shows a larger protrusion on rod than I set up, so thanks to all, that should do it.