mazda mpv brakes

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cselby@mts.net - 05 Jan 2008 05:09 GMT

I've been a licenced mechanic since 1971 and I am since retired and
have forgotten something obvious about brakes.

My kids Mazda MPV 4WD with rear wheel "ABS" has a low brake pedal. I
took the master cyl off and stripped it down, washed it out, rubbers
looked good, cylinder clean and smooth, re-assembled and began to
bleed the brake system. I got no improvement in the brake pedal -
still way too low.

Rear drums removed, shoes & hydraulics inspected, brakes adjusted
manually to "just" rubbing. Front pads will need replacement
sometime this summer, but still serviceable. No leaks in any of the
cylinders or calipers. Rear brakes bleed on the left side only - the
right side has no bleeder, but another line going to the left side
which has the bleeder. There is a bleeder on the "ABS" module that
feeds both rear brake cyls.

I must be missing something really obvious, and I can't for the world
of me think what. Before I go and strip everything down to nothing,
I need someone with the "obvious" answer.

Thanks

Pete

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Doug Adams - 05 Jan 2008 18:41 GMT

You say there is no bleeder on the right side? You always need to bleed
both wheel cylinders, starting with the one with the longest line (furthest
from the master cylinder). I have had cars that the only way I could get
them to work was with a pressure bleeder. How are you bleeding the system?
The best way is to have someone press the pedal, crack open the bleeder a
little, when the pedal goes down to almost bottom have the person say "O.K."
and tighten bleeder. Make sure they don't let up on the pedal till you say
"O.K." that you have the bleeder tight. Repeat the process until the pedal
gets better. Are you sure you have air in the line? Usually the pedal will
be spongy with air in it. You may need to bleed a pint or so of fluid off
to get all the air out. If the air is close to the master cylinder it will
have to be pushed all the way out of the wheel cylinders.
I think the problem is really in the right rear with no bleeder,
probably was twisted off at one time. In that case you should probably just
replace the wheel cylinder and save yourself a lot of grief.

> I've been a licenced mechanic since 1971 and I am since retired and
> have forgotten something obvious about brakes.
[quoted text clipped - 20 lines]
>
> Pete

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cselby@mts.net - 05 Jan 2008 19:07 GMT

> I think the problem is really in the right rear with no bleeder,
>probably was twisted off at one time. In that case you should probably just
>replace the wheel cylinder and save yourself a lot of grief.

Thanks. The right side has no bleeder. It has a brake line going in
and one going out to the left side. The rear brakes are in series
with the right side feeding the left - and then a bleeder. Bleeding
the rear brakes at the left, bleeds them both.

I've bleed about a liter of fluid so far and I'm still missing
something.

Pete

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Doug Adams - 06 Jan 2008 18:17 GMT

> Thanks. The right side has no bleeder. It has a brake line going in
> and one going out to the left side. The rear brakes are in series
> with the right side feeding the left - and then a bleeder. Bleeding
> the rear brakes at the left, bleeds them both.

O.K then if the right side is being fed first does the line go in the bottom
of the cylinder and then out the top to the left? I could see that if it
were the other way around air would remain trapped in the top of the right
side cylinder when bleeding the left. Air always stays in the top of any
container if fluid is pushed in and the bottom is opened up then the fluid
would be pushed on through and the air would remain trapped. I would think
it would be very important that the line coming from the master cylinder is
going into the bottom of the cylinder and the line going to the left is
connected nearest to the top. Maybe somebody replaced these lines one time
and reversed them?

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benteaches@gmail.com - 07 Jan 2008 15:42 GMT

On Jan 4, 11:08 pm, cse...@mts.net wrote:

> I've been a licenced mechanic since 1971 and I am since retired and
> have forgotten something obvious about brakes.
[quoted text clipped - 20 lines]
>
> Pete

Keep bleeding... bleed all the bleeders, especially the ones on the
abs components.
Start the engine and pump the pedal while running, then bleed again.
HTH,
Ben

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