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Old 04-03-2004, 01:00 PM
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at wits end on ford brakes.......

hey all, pulling hair here..... 72 f250 2.5" drum all the way around.
new master cylinder.
new vacuum booster.
new wheel cylinders x 4
new rubber lines at the wheels.
new shoes.
turned drums.
new internal hardware.
speed bleeder screws.

only thing i didn't replace was the steel lines......

brakes have been bled to the tune of 2 quarts of dot 3 fluid being run through in an effort to ensure NO air or old crap remained.....

still no brakes. i have the vac. booster hooked up to manifold vacuum, maybe i should run it directly to the carb? stock was to man. vac., but the brakes didn't work worth a crap then either.....

just thinking outloud here, and welcome any input.....

i'm ready to pay a shop to do this...... fn wussy

edit, adjusters are all the way, ie, when you spin a wheel, you can hear the shoe rubbing the drum, so i don't think it's backed too far off...... wth?

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Old 04-03-2004, 01:07 PM
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does your emergency brake work??
im not all that familiar with 4 wheel drum but with all the work you did it sounds like you need better vacuum.
is the pedal hard or soft?
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Old 04-03-2004, 01:38 PM
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Arrow

-Brake Troubleshooting-

Adjusting Drum Brakes-

Run the shoes up until you hear a distinct rubbing on the drum. Press the brake pedal down to center the shoes on the backing plate. Readjust until you can only spin the tire from 3/4 to 1 full turn with moderate effort. The self adjusters will take it from here unless the arc of the shoes are far from the arc of the brake drum. In this case, you will have to manually adjust again until the two surfaces are evenly identical.
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Old 04-03-2004, 04:26 PM
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e-brake works......
with motor off, the pedal gets firm.
motor on, goes to the floor, but pumps up, not very well though.......

gonna check for the residual valve........
thanks guys.
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Old 04-03-2004, 06:07 PM
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like i said im no 4 wheel drum guenius but if the pedal is soft when you start it and you dont have any brake fluid leaks i would say you have a vacuum leak.
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Old 04-03-2004, 06:48 PM
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Well i'm no genius period, but wouldn't a vacuum leak of that size at least have an audible hiss?....... only thing i hear over the cam and my one header leak, is the smooth sound of power. oh, and me screaming through the next intersection.............
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Old 04-03-2004, 08:00 PM
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Question

Quote:
Originally posted by crazy larry

...wouldn't a vacuum leak of that size at least have an audible hiss?....... only thing i hear over the cam and my one header leak, is the smooth sound of power. oh, and me screaming through the next intersection.............
Uh...How large of a cam do you have? Have you put a vacuum gauge on it to measure actual manifold vacuum? It needs a minimum of 18" to work properly.
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Old 04-03-2004, 08:13 PM
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whats a vacuum gage?

No sir, I haven't put a vac gage on it, it's a e-brock performer cam....not too radical. not too radical at all.......
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Old 04-03-2004, 09:31 PM
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Did you bench bleed the master cyl?

Quote:
Originally posted by KULTULZ
Have you put a vacuum gauge on it to measure actual manifold vacuum? It needs a minimum of 18" to work properly.

Uh, no it doesn't. A lot of engines don't even have 18" of vac.
My truck idles at 16" in N and 14" in drive. My brakes work fine.

Last edited by FASTCHEVY; 04-03-2004 at 09:31 PM.
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Old 04-03-2004, 10:20 PM
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Cool

Quote:
Originally posted by KULTULZ

Have you put a vacuum gauge on it to measure actual manifold vacuum? It needs a minimum of 18" to work properly
Quote:
Originally posted by FASTCHEVY

Uh, no it doesn't. A lot of engines don't even have 18" of vac.
My truck idles at 16" in N and 14" in drive. My brakes work fine.
-Master Power Brakes Booster Tech Info-

Quote:
Q How much vacuum is needed to operate a booster properly?

A For a power booster to function properly you will need at least 18" of vacuum. Anything lower will give you a hard pedal.
Hmm...I see. I guess the industry has been wrong all these years. I guess vacuum reservoirs and vacuum pumps are completely useless here. Hydro-Boost is just an expensive add-on.

I will noyify the fine folks at MPB and cam manufacturers of your findings.

I guess all he really needs is a hose leading to the passenger compartment and he can suck on it when he is contemplating a stop. Of course he will suck harder and suck more seat cover once something stops or pulls immediately in front of him...

Quote:
..me screaming through the next intersection.............
E-MAIL FASTCHEVY when out of the hospital....

Thank You for the clarification on the subject...
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Old 04-03-2004, 10:44 PM
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you don't need 18 pounds of vacuum to run power brakes.
you just need a nice vacuum canister.
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Old 04-03-2004, 11:03 PM
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Question

...why me?
________________________________________________

Whoops!

Sorry...Thought you were FASTCHEVY...

I must remember to read and comprehend before hitting the submit button...
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Old 04-03-2004, 11:05 PM
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oh c'mon im just foolin around. i know you need 18 pounds of vacuum. i's be dooin me readin.
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Old 04-04-2004, 03:11 AM
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Sounds like your pressure differential valve is stuck at one end Larry, on the old Fords the valve has a pin that needs centering so that the brake light goes out inside the cab. If that plunger is stuck all the way to one end or is corroded and stuck you will have no brakes at one end...and a light inside the cab that won't go out.

The procedure to center the valve is simple, bleed the brakes and then after bleeding one end, release a little from the opposite end (Front or Rear) to get the light to go out inside the truck (while applying the brakes). If the light doesn't work you will need to fix it or use an ohmeter on the harness coming from the valve. Hopefully it's not seized up or the pin sensor shot, you will have to check. Not sure where you can get a rebuilt unit, an adjustable one is a nice upgrade but you lose the light on the dash telling you the brakes are out. Not that you need that stupid light to tell you anyway. The valves are supposed to be self centering and have a spring inside, but with age many are seized up. When they were new all you had to do was apply the brakes and it would self-center. The idea was that if one end developed a leak the plunger would move to block the port on the leaking side, turn on the light inside the cab and apply full hydraulic pressure to the good side.

This was the only site I could find that sold repro units, they look nice made of brass.

http://www.inlinetube.com/pro_valves.htm



For the money I would get a plain adjustable like this one,



...and plumb it into the rear brake line. You can just use a coupler for the fronts. Remember to take it out for a test drive and set the adjustable valve with an empty load under full braking from speed, wouldn't want the rear overtaking the fronts in a panic stop.
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Old 04-04-2004, 03:47 AM
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Quote:
Originally posted by KULTULZ
Uh...How large of a cam do you have? Have you put a vacuum gauge on it to measure actual manifold vacuum? It needs a minimum of 18" to work properly.

Here is some real info from a real website, read par 6. www.cranecames.com/pdf/

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