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Discussion Starter #1
On my 97 F350 my brake pedal is very hadr to push down and does not return once applied. Under throttle the pedal is slowly pulled to the floor. I recently replaced my vacuum pump because it went bad now I am having this problem.
 

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Sounds like you have serious Master cyllinder / Booster problems. Unplug the booster and see what happens. If the brakes work but are hard it is the booster. Other than that I would replace the Master ( assuming all is bled correctly and you have no obvious leaks and the fluid is good )
 

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Discussion Starter #3
I pulled the vacuum line from the booster so i could get a load of wood a couple days ago and the pedal quit going to the floor. But as expected the brakes were very weak. I replaced the booster 4 years ago but have only driven the truck 5,000 miles since.
 

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It could....

It could be bad again. Stranger things have happened. Booster is also my guess for the symptoms you're describing.
 

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Discussion Starter #5
It seems like since I quit driving this truck all the time parts that I had recently replaced on the brake system keep going bad. The last vacuum pump had less than 10,000 miles on it.
 

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If I recall the rules correctly:

- hard pedal = bad vacuum pump or vacuum leak
- soft pedal = air in lines, bad fluid, leak in brake lines, bad master cylinder

I've replaced the vac pump several (3,4,5 times?) in the 101k miles I've owned the truck. Would love to go to hydroboost brakes but no room in the budget right now...
 

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Did you put a vacuum gage on it to see how much you have IIRC you need at least 10.5 inches of vacuum for booster to operate. Just my .02
 

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Maybe you bought Chinese made parts. I used to, Not anymore . Now , I only buy Made in USA or Canada , OR Rebuilt locally . . . No Mexico / Brazil /China etc. It costs a bit more but they last longer.
 

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I vote for Booster, especially if the pedal gets "pulled" to the floor. Get the zer-loss booster for a replacement.

Brake Booster, Zero-Loss (94-97)
(Ford) F5TZ-2005-CA (not a service replacement; it must be ordered by the part number, not vehicle application … from TSB 96-25-19, but TSB number not verified)

Cheers!
 
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