New brake booster question, '86 F-150

Hello,

I have an '86 F-150, rear wheel drive, manual trans, inline 6.
Recently the brake booster was hissing, so I replaced it. Lately I
have noticed the brakes feel very different.

1. When travelling 25 MPH or higher, pressing the pedal to stop more
suddenly, there is good pressure until about halfway down, then the
pedal travels more easily and doesn't feel like it has much pressure
(pumping it seems to build up some pressure). At the point the pedal
does not have pressure, the brakes seem to brake harder (as if the
pedal was really being pushed down hard).

2. When travelling really slow, 5 MPH or so and I lightly apply the
brakes to stop, the pedal travels just a little ways then the brakes
just suddenly lock up (again as if the pedal was really being pushed
down hard).

3. From time to time the brakes (I think the front) do not seem to
open up all the way, as there is a slight drag. This is more
noticeable when stopping on a slight incline, the vehicle does not
roll forward or backward when it should.

Does this sound like a faulty brake booster? Or does the booster need
to be adjusted (in which direction)? I didn't notice this behavior
with the old booster, and I have checked the fluid level and it is
fine.

Thank you for all feedback, and help!!!
--
Chris

Chris Szilagyi wrote:

> Hello,
>
> I have an '86 F-150, rear wheel drive, manual trans, inline 6.
> Recently the brake booster was hissing, so I replaced it. Lately I
> have noticed the brakes feel very different.
>
> 1. When travelling 25 MPH or higher, pressing the pedal to stop more
> suddenly, there is good pressure until about halfway down, then the
> pedal travels more easily and doesn't feel like it has much pressure
> (pumping it seems to build up some pressure). At the point the pedal
> does not have pressure, the brakes seem to brake harder (as if the
> pedal was really being pushed down hard).
>
> 2. When travelling really slow, 5 MPH or so and I lightly apply the
> brakes to stop, the pedal travels just a little ways then the brakes
> just suddenly lock up (again as if the pedal was really being pushed
> down hard).
>
> 3. From time to time the brakes (I think the front) do not seem to
> open up all the way, as there is a slight drag. This is more
> noticeable when stopping on a slight incline, the vehicle does not
> roll forward or backward when it should.
>
> Does this sound like a faulty brake booster? Or does the booster need
> to be adjusted (in which direction)? I didn't notice this behavior
> with the old booster, and I have checked the fluid level and it is
> fine.
>
> Thank you for all feedback, and help!!!
> --
> Chris

Sounds like you need to adjust the free travel somehow...

nate

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"Chris Szilagyi" > wrote in message
m...
> Hello,
>
> I have an '86 F-150, rear wheel drive, manual trans, inline 6.
> Recently the brake booster was hissing, so I replaced it. Lately I
> have noticed the brakes feel very different.
>
> 1. When travelling 25 MPH or higher, pressing the pedal to stop more
> suddenly, there is good pressure until about halfway down, then the
> pedal travels more easily and doesn't feel like it has much pressure
> (pumping it seems to build up some pressure). At the point the pedal
> does not have pressure, the brakes seem to brake harder (as if the
> pedal was really being pushed down hard).
>
> 2. When travelling really slow, 5 MPH or so and I lightly apply the
> brakes to stop, the pedal travels just a little ways then the brakes
> just suddenly lock up (again as if the pedal was really being pushed
> down hard).
>
> 3. From time to time the brakes (I think the front) do not seem to
> open up all the way, as there is a slight drag. This is more
> noticeable when stopping on a slight incline, the vehicle does not
> roll forward or backward when it should.
>
> Does this sound like a faulty brake booster? Or does the booster need
> to be adjusted (in which direction)? I didn't notice this behavior
> with the old booster, and I have checked the fluid level and it is
> fine.
>
> Thank you for all feedback, and help!!!
> --
> Chris

Sounds like the booster is bad. Give it a look over first, then replace it
if you find nothing wrong.


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That was the problem, the master cylinder pushrod was not at the
correct spec. According to my Haynes manual, it should be out
..980-.995 inches from the body of the booster. Got this adjusted
properly and all is well now! All of the problems seem to have gone
away.

Thank you very much for all feedback and help!!

--
Chris

"Tegger®" > wrote in message > ...
> (Chris Szilagyi) muttered darkly in
> m:
>
> >
> > 3. From time to time the brakes (I think the front) do not seem to
> > open up all the way, as there is a slight drag. This is more
> > noticeable when stopping on a slight incline, the vehicle does not
> > roll forward or backward when it should.
>
>
>
> Master cylinder pushrod free play is wrong. Needs to be adjusted.
>
> The pushrod is not moving back far enough to allow the return port to open
> properly.
>
>
> --
> TeGGeR®
>
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