excessive brake travel - brake experts

I'm stuck, I have a 1995 del sol vtec with ABS. 4 wheel disks. I've
been driving it like this for a month, but can't help but be concerned
for my safety.

I bled the brakes several times following procedures in helms+chiltons.
I'm 99% sure there is no air in the system. I went through 2 bottles of
motomaster crap, and 1 honda dot3.

recently i bought a haynes. it mentions NOT to bleed honda's equipped
with ABS as you need proper tools. this is the first i've heard of
this. can anyone confirm that?

now, my brakes are engaging, but at a much lower pedal height. the MC
is not leaking.
with the engine off, subsequent pumps raises the brake pedal height,
quickly (3X).
with the engine ON, the pedal height doesn't increase with more pumps.
(however, I remember it did prior to bleeding, so I'm guessing this is
abnormal)

i can apply steady pressure to the brake pedal and it doesn't sink. (mc
good) Following instructions in haynes I determined my booster is good.
Brake pedal is engaging very low. If I push VERY hard on the pedal I
can feel rock bottom of it's travel. the vehicle doesn't pull to a side
when braking.

a 70 kph - 0 (pedal to floor) brake will engage ABS very briefly at the
end, but I definateloy feel I have lost some braking performance
compared to what I had previously.

hmmmm? i'd appreciate any thoughts!

 

the master is leaking internally, the abs system is independent on this car.
replace the master!
Chip

 

==================

Did you bleed them after dumping all vacuum, by tapping the pedal a few
times, then going front-left, front-right, rear-right, then rear-left ?
Did you get a helper to push the pedal gently while you opened the
nipple, or use a Mity-Vac, or a pressure bleeder?

There's much disagreement out there . . . :-(

'Curly'

 

the master has two pistons, each serving a front & rear brake, arranged
one behind the other in the cylinder. when the seals on both pistons
are ok, hydraulic pressure from the first presses the second. if one
fails, one piston sinks until it bottoms out against the end of the
cylinder or against the other piston before it starts to build pressure,
hence the excess travel. it also means you're not getting proper
braking on 2 of your 4 wheels.

to cure, replace the master cylinder. the abs just modulates the
pressure supplied by the master.

if you want to be confident of factory bleed procedure, follow the helm
manual instructions - ignore the others.

 

bled them in the sequence according to helms. by the book all
procedures followed. (submerged in clean brake fluid bla bla bla) i
think it was rear right, left front, right front, rear left. yep had a
helper. we pumped about 4X in between bleeds. (pump 4X and hold pedal
down, unscrew bleed bolt, wait 5-10 seconds watch fluid for air,
retighten, then begin again.) bled each wheel 7 times. i wouldn't
really call it gentle pedal pushing though. not rough, but moderate
pumping. we held it as far down as it would go. (pedal height will
continue to drop when bleed bolt released)

i have heard afterwards that when bleeding not a good idea to go pedal
to metal. gritty deposits etc in MC could cause seals to crack, chip
when the piston goes in that deep. oh well.

the diagnosis you said about only one of my pistons in the MC
functioning was somewhere along the lines I was thinking. this is
pretty much what it feels like. however, my MC or reservoir doesn't
show any signs of leakage. could this situation still exist if that
were true? why would hydraulic pressure not be increasing with
subsequent pumps even if one of the pistons was functioning?

any suggestions on how to test my MC? maybe i'll head out to the
junkyard and see if I can find another one. or better yet, i'll check
out the prices of new MCs. this is a critical component.

thanks...

 

If fluid comes out of all four wheels when you bleed them, both pistons in
the MC are at least doing something. Haynes is wrong about the tools. No
special tools are required to bleed brakes on this generation of Honda.
When you bleed it, the cover on the MC should be off and you should close
the bleeder as soon as the pedal is down. Then pump it back up with the
bleeder closed.

Did the fluid level in the MC drop below the visible part of the reservoir
at any time while you were bleeding? If so, there could be air in the MC.
Try cracking the brake line connections at the MC (one at a time, fill cover
off) and pump it a couple of times to make sure there is no air trapped in
it.

What is the condition of the pads? If they are near replacement time, that
alone can account for a low pedal.

It is not a given that the MC is now bad because you pumped the pedal all
the way down, but a bad MC is a possibility.

Another possibility - if the MC was replaced at some point in the past and
the piston between it and the booster was not properly adjusted could set a
permanently low pedal engagement point. If the pedal is solid otherwise but
just low, this might be a cause.

For the immediate problem - if the only thing you did was bleed the brakes
and that resulted in the soft pedal you now have, I think there is at least
a 50-50 chance that you introduced air into the lines doing the bleeding.
Try again...

Btw - it has nothing to do with this problem, but you should also change the
fluid in the ABS. The procedure is in the Helms book.

 

yes fluid came out of all four wheels when bleeding. i bled the brakes
twice. 7X each time. (two seperate ocassions) because it was always a
low pedal. i will do it again.

the level in the MC reservoir was always above the min. level. and the
pads are in great shape. MC looks original 'nissin' oem. don't think
its ever been replaced.

according the haynes. a low brake pedal = partial brake system failure.
haha. wtf is that suppose to mean? jee thanks.

i just want to quote you here:
Try cracking the brake line connections at the MC (one at a time, fill cover

sounds interesting. what exactly do you mean by 'cracking'?
....pinching? i'd appreciate any details you can provide to bleed the
MC. thanks a lot for your help!

andre

 

I had the same experience with my 86 Accord once. I finally rebled after
driving it for a while for any residual air bubbles that are trapped to
settle. That seemed to have solved the problem. It turned out that in my
case, I somehow accidentally introduced air into the system.

 

It just means some part of the system (one of the wheel cylinders/calipers,
or one of the the two circuits in the MC) isn't working.

It would be hard to pinch a metal brake line without destroying it. I meant
loosen the nut holding the brake line to the MC just enough for fluid/air to
escape when you push the pedal down, Use one of those open end wrenches that
wraps almost all the way around the nut when you do it. It is pretty easy
to mess up the nuts and then you have to fix the end of the brake line (not
fun).