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Author Topic:   power drum brakes
KenH
Journeyman

Posts: 6
From:
Registered: Apr 2004

posted 04-09-2004 12:36 PM     Click Here to See the Profile for KenH   Click Here to Email KenH     Edit/Delete Message   Reply w/Quote
Is there anybody out there with a running
torino or other ford with power drum
brakes?

I am running power drums on my 71 torino.
New master cylinder, new brakes and hardware
good strong vacuum from booster.

I have no leaks, professionally power bled
brakes.

Still have a very sensitive pedal. my
mechanic says that is what ford power
drums were like.

The pedal is light to touch, does nothing
until about the last 1-2 inches of pedal
travel. If you slam on the brakes they
lock up. basically the upper portion
of the pedal travel does nothing.

(I know I need disc brakes)

thanks for any help.
ken

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SteveLaRiviere
Administrator

Posts: 44921
From: Saco, Maine
Registered: May 99

posted 04-09-2004 03:25 PM     Click Here to See the Profile for SteveLaRiviere   Click Here to Email SteveLaRiviere     Edit/Delete Message   Reply w/Quote
Sounds like you need to adjust your brake bands. They have lots of travel when the linings aren't up to to the drum closely. Did your mechanic try adjusting them?

------------------
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KenH
Journeyman

Posts: 6
From:
Registered: Apr 2004

posted 04-09-2004 06:13 PM     Click Here to See the Profile for KenH   Click Here to Email KenH     Edit/Delete Message   Reply w/Quote
The pads are mostly new, have been adjusted.

The brakes begin to work high in the pedal
travel when the vacuum is unhooked, which
has me very confused.

the booster is a used unit. I could see
a bad unit making the pedal sensitive but
shouldn't really effect the pedal travel.

thanks.
ken

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KULTULZ
Gearhead

Posts: 834
From: Rockville, MD
Registered: Oct 2002

posted 04-09-2004 06:58 PM     Click Here to See the Profile for KULTULZ   Click Here to Email KULTULZ     Edit/Delete Message   Reply w/Quote
Was this car manual drum or power drum from the factory?

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KenH
Journeyman

Posts: 6
From:
Registered: Apr 2004

posted 04-09-2004 08:12 PM     Click Here to See the Profile for KenH   Click Here to Email KenH     Edit/Delete Message   Reply w/Quote
manual drum brakes. I don't detect any
pressure leaks or hissing noise coming
from the power booster.

Even if I learn to use a light touch, which
by itself is a dangerous idea, the brakes
only work in the last 1 or so inches of
pedal travel towards the floor.

thanks.
ken

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MLariviere
Moderator

Posts: 4063
From: Biddeford,Me.USA
Registered: May 99

posted 04-09-2004 08:55 PM     Click Here to See the Profile for MLariviere   Click Here to Email MLariviere     Edit/Delete Message   Reply w/Quote
Did you use the right pedal support? There may be a difference with them.

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KenH
Journeyman

Posts: 6
From:
Registered: Apr 2004

posted 04-09-2004 09:12 PM     Click Here to See the Profile for KenH   Click Here to Email KenH     Edit/Delete Message   Reply w/Quote
I have to believe that the all the
mechanical connections are correct since
the brakes work as expected with the
vacuum unhooked.

Has anyone used residual valves for power
drum brakes?

Check this out, look for the setup with
drum/drum:
http://www.mpbrakes.com/mpfaqvalving.htm

It uses two residual valves.

thanks.
ken

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KULTULZ
Gearhead

Posts: 834
From: Rockville, MD
Registered: Oct 2002

posted 04-09-2004 11:38 PM     Click Here to See the Profile for KULTULZ   Click Here to Email KULTULZ     Edit/Delete Message   Reply w/Quote
Kevin,

The actual brake pedal is the same regarding manual and power brakes, so that won't be the problem. There is however a difference in the master cylinder (15/16" bore for power and 1" bore for manual). If you retained the manual master cylinder, the booster could slam the extra bore capacity to the wheel cylinders. There is also two different power boosters, drum and disc. I would think the disc is more agressive. Do you know that you retrofitted the correct booster and master cylinder on the conversion?
________________________________________

I re-read your description and you are describing overly sensitive pedal with excessive pedal travel with boost? The overly sensitive pedal most likely is resulting from a condition described above but excessive pedal travel indicates excessive shoe movement. This may be from improperly adjusted brakes or as a result of the brake linings not making full contact with the brake drum surface. They may need wearing in to get the proper contact.

There also may be a problem with the master cylinder push rod not being adjusted as needed. This is described in the shop manual.

Your car is equipped with a combination valve and the residual valves will be incorporated in that. There may be a possible failure of the valve itself and the manual will have a diagnostic routine for that.

The MPB website has a good flow chart to diagnose brake problems.

http://www.ucx.com/flowchart.pdf

[This message has been edited by KULTULZ (edited 04-09-2004).]

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