Let me see how I can start answering your questions.
Low Pedal:
The low pedal can be that all the shoes are not adjusted properly "close to
the drums" Therefore the pedal has to travel further pushing more fluid into
the wheel cylinders to bring the shoes into contact with the drums. I'd
check all the drums again to be sure that when you rotate the wheel each
shoe is lightly contacting the drum. This will raise your pedal height.
Brake Drag:
Brake manufactures make brake shoe linings of different thickness to
compensate for turned drums and you just may have a set that's thicker than
the standard thickness?
I'd have all the drums turned just to make sure there all perfectly round.
They sell an inexpensive brake shoe adjusting tool at local auto part stores
to help set the proper clearance.
You also need to pay close attention to the wear tabs on the backing plates
"where the brake shoes contact" for wear groves. If the tabs have groves,
they can keep the shoes from operating properly i.e.., dragging or not
applying correctly! I just weld up the groves and grind the surface flat
again. You then need to apply some White Grease to the wear points on the
backing plates and the adjuster when you install the shoes.
Decreasing Pedal Height:
>From your description of the decreasing pedal height, you have an internal
leak in the master cylinder that is allowing the fluid to leak past the cup
and back into the reservoir. I've had this problem on more than one
occasion and had to put a rebuild kit in the master cylinder.
A quick check for this would be to pump the pedal up 8-10 times and hold the
pedal down. If the pedal slowly continues to go down you have an internal
leak in the master cylinder.
I'd replace or rebuild the master cylinder first, bleed the brakes again and
have the drums turned down. Then I'd buy the brake adjusting tool to
properly set the brake shoe clearance.
Joe
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----- Original Message -----
From: Hollis Troop12 <hollisbsa@hotmail.com>
To: <oletrucks@autox.team.net>
Sent: Monday, March 20, 2000 9:25 AM
> This is try 92 to get a message to post - I am now trying our local boy
> scout hotmail account - hope this one works.....
>
> sorry list!
>
>
> I have a 46 1/2 ton. I have rebuilt all of the wheel cylinders and the
> master cylinder. The truck was on jacks stands and mostly level. Well I
> was able to bleed the lines using a one man bleed kit. It has a magnet
and
> the draining bottle sticks to the wheel well above the cylinder. It seem
to
> worked - took out all of the black fluid and once it started running clear
> with no air I turned off the bleeder valve and replaced the screw. Off to
> the next wheel - all of them with the same result.
>
> However, I can not sustain any pressure on the break pedal. I can pump it
> up (8 - 10 times) and it will be firm for the bottom 1/3 of the press to
the
> floor. After 30 seconds this pressure is loss as well. I have placed the
> wheels back on the truck and moved it to a very level spot. There is no
> leakage of break fluid form anywhere I can detect. I will try to re-bleed
> the wheel cylinders again.
>
> Any suggestions?
>
> Second issue. I have purchased new break shoes and placed them on the
> truck. To start with I have turned the wheel cylinder/pad attachment
screws
> all the way in. The rear wheels still drag on one spot in each
revolution.
> I know I need to get the drums turned. If this will not take care of the
> drag what should I do? I purchased the break shoes from Carter and they
> assured me they were the correct size. I have matched them up with the
old
> shoes and the look to be the same to me. Any hints would be appreciated.
>
> Thanks
>
> Jim House
>
>
> oletrucks is devoted to Chevy and GM trucks built between 1941 and 1959
>
oletrucks is devoted to Chevy and GM trucks built between 1941 and 1959
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