Brake Pedal still mushy after brake job

er, no. "aluminum" covers many hundreds of alloys and alloy products.
some corrode, some don't. brake cylinders don't corrode internally
until the fluid is /way/ contaminated. i got a cylinder from a junkyard
that had been exposed to rain - top of the reservoir off and full of
water - for months. the inside was gummed up with decayed rubber, but
it cleaned up and worked just fine with a new seal kit in it.

now, you can get a problem where the steel piston and aluminum cylinder
have an electrolytic corrosion issue, but that doesn't effect the
sealing surface down the cylinder wall until it's at a really advanced
stage.

steel cylinders otoh, /those/ things are famous for corrosion.
especially on the bottom of the cylinder where moisture collects.

the black dots are usually just rubber.

that's good advice - no need to push contaminated junk through the whole
system.

no, i mean panic stopping, not using the hand lever.

ok, now you're really pulling stuff out of your ass.

http://www.sealingspecialties.com/materials.htm

eh? yes they do wear, but do your homework! swelling & shrinkage is
absolutely an issue. you're expressing opinion as fact, and that
opinion is ill informed!

 

Ya got lucky. It takes time for corrosion to start.

Nope. Corrosion. A pick will hang up in the holes. Seen it often enough,
even in clutch master cylinders.

No corrosion, no dots.

If the fluid is that bad, the rest of the system is already in trouble.

Then what I said.

You're right. My memory is bad. I thought I had read they were neoprene.
Been years since I looked that up.

Looks like the actual stuff is ethylene propylene.

Sorry, the seals do not "swell". Unless the fluid gets contaminated with
oil.

Brake fluid is designed to prevent swelling, and seal materials are not
water soluble.

 

eh? where do i ever mention pressing to the floor in panic stopping???
normal braking gets you maybe 20% of travel. i doubt panic gets you 50%.

that's more ill informed opinion, not fact.

"_Elastomer Swelling_
The elastomers employed in the brake system must be able to adapt to the
type of brake fluid being used. Although a small amount of swelling is
desirable, it is imperative that it not exceed a rate of approximately
10%. Above this figure, the brake fluid has a negative effect on the
strength of the elastomer components."

isbn 0-8376-0333-1, p242.

"Even minute levels of mineral-oil contamination (mineral-oil-based
brake fluid, solvents) in glycol-based brake fluid can lead to
destruction of rubber components (such as seals) and ultimately lead to
brake-system failure."

isbn 0-8376-0333-1, p242.

it /is/ designed to cause a degree of swelling as that improves sealing.
just like it's got to lubricate, inhibit corrosion, and resist
boiling.

where do you get water solubility from???

 

Thanks for the link.

 

No, NOT for ALL Hondas. Once again, my 99 Prelude Service Manual (Published
by Honda Motor Co, Ltd, Service Publications Office, P/N 61S3002, 1384
pages -- ie. "Helms") clearly states and shows the diagram on pg 19-7 that
the sequence is
1) LF,
2) RF,
3) RR,
4) LR
for this split diagonal braking system. This ABS system uses the single
brake reservoir typical of most recent systems.

The original poster has a 91 Prelude which is probably similar to my
previous 90 Prelude ALB (first year Honda offered ABS under the Honda badge)
and as the OP indicated, has a second reservoir for the ABS function.
Therefore, I will not assume which bleeding sequence should be followed in
that case.

J.

 

The article at that link was very interesting -

Here is what I think I may start doing:
At every oil change I will get out the Turkey Baster, suck out the
master cylinder reservoir and put in clean brake fluid. By doing this I
will regularly reduce the amount of water, eliminate some contamination,
and replenish the corrosion inhibitors that may have become depleted. I
also will avoid all the the work and pitfalls of bleeding the system,
including damage that may or may not be caused by master cylinder piston
travel. My system will never be as clean as it would have been right
after a complete flush, but it will always be cleaner than it would have
been in the second year of a two year cycle. The cost would be minimal.

 

it's an interesting idea and certainly better than doing nothing. not
sure about the frequency thing, but again, doing it is better than nothing.

what it doesn't achieve is flushing the fluid in the brake calipers and
the rest of the system. i understand that the primary source of
moisture in the system is diffusion through the flex hoses - and if
you're reconditioned many calipers, you will have seen some disgusting
muck & rust accumulation resulting from that. other than a strip-down &
reconditioning exercise, the next best way to keep calipers in good
condition is to flush them out.

 

Diffusion which way? In or out?

 

in. if moisture [water] were diffusing out, it would be a self-purging
system. brake fluid is strongly hygroscopic.

 

The source is the master cylinder, not the hoses. The master cylinder has
this great big opening on top, capped with a vented rubber chapeau. Air
enters there, along with whatever moisture it carries.

Water is heavier than brake fluid, so it travels downhill, eventually
ending up in the calipers and wheel cylinders. That's why the black
corrosion dots are always at the bottom of the bores.

The hoses are quite impermeable, you may believe me on that.

 

in terms of surface area to volume ratio, the flex hoses are a bigger
source.

i don't believe you - i'm the materials guy.

for a simple explanation, check

http://www.stoptech.com/tech_info/wp_brakefluid_1a.shtml

about half way down.

 

The other problem is that as you brake, fluid is constantly mixing
around. I did a full flush of my system, and yet soon saw some rust
evident in the master cylinder (got the vehicle used, and it may never
have been fully flushed--the front calipers had quite a bit of rust in
the bore). I probably didn't get evry last bit out of the calipers
during the flush, but my point is that there is a lot of fluid
circulation, and sucking out the master cylinder every 3-4 months
(assuming you're very good about changing your oil) is going to leave a
lot of crud in the rest of the system.

Abe

 

well, if you want to be really anal about it, take the m/c off, strip it
down and clean it out by hand. it's no less of a task than doing a
caliper. i did the whole system on my 89 when i first got it. only
thing i didn't touch was the proportioning valve.

another tip: if badly crudded up, bleed the master cylinder at the
outlets, DO NOT force dirty fluid the whole way through the system.
this is another reason to do bleeding using the full piston stroke - it
forces all the sludge out rather than let it continue in residence. but
a strip-down would be better.

 

Not from what I'm reading.

http://www.gs610.com/abc.htm
Excerpt:
"It depends on the fluid and environment. A typical high performance DOT 4
fluid like, Motul, AP, Castrol SRF, Wilwood and ATE SuperBlue, in a high
humdity evironment will absorb as much as 4.5-5% moisture in as short a
period as 2 weeks. In real world testing (several daily driver cars,
Prospeed GS610™ absorbed <1% moisture in 3 years. This was measured from
the brake fluid in the resevoir where the vehicle's brake system is most
likly to contain the greatest contaimination of moisture."

and see under the paragraph "How does brake fluid become contaminated?".




Not quite...

It turns out some of them /do/ absorb water, but not those on Hondas and
other Japanese makes.

My mechanic tells me Honda hoses are made of special rubber that does not
allow fluid intake. He doesn't know what it was called or when they started
using it, but it's probably "EPDM" according to what I'm finding in Google.

Apparently the hose water absorption thing is now largely a thing of the
past.

Yes, but higher up they say:

"The fluid in the system absorbs water through the breathers, through the
caliper piston seals and by magic."

and

"The magic of diffusion allows moisture in the air to permeate microscopic
pores in the rubber brake hoses, the nylon master cylinder reservoir, and
the various rubber seals in the hydraulic system. Sadly, there is nothing
we can do about it and if left unchecked the water would sit in our brake
system and rot it away from the inside out."

So the hoses are only one small part of the absorption. If you count the
hoses for absorption, you have to count EVERYTHING.

Contaminated fresh fluid, and the master cylinder are the main sources.

 

:

That's an excellent idea. Except if you're going to do all that, you might
as well replace the seals, and by that point it's probably easier (and not
much more expensive) to just replace the MC entirely.

All my brake hydraulic problems disappeared when I started doing annual
fluid changes (with my Integra in '91). Prior to that I had the same
problems everybody else here reports.

It baffles me why more is not made of annual fluid changes, especially when
you consider that your brakes are you last line of defense against crashing
itno things.

It also amazes me that brakes continue to work as well as they do
considering the astonishing level of neglect and abuse they have to endure.

 

er, you want me to regard as authoritative the word of some dude selling
"Prospeed GS610 Maximum Performance Brake Fluid"?

where do you get this stuff??? read some of the material spec sheets!!!
the rate of diffusion is different for different materials, but it
still occurs! and you're not paying attention to surface area/volume
ratio either.

so, your mechanic knows more about materials...

fluids are better and hoses are better, but DIFFUSION cannot be eliminated.

that's dumbed down... and apparently with good cause since "diffusion"
seems to be such a freaky concept.

yes, you have to count everything, but i say again, do the math on the
surface area of the hoses and figure out how that compares.

whatever.

nothing irritates me more than people that don't know quoting other
people that don't know as if they're authoritative. whatever happened
to reference libraries? has everyone forgotten what text books are for?
what happens if an authoritative reference text is not online?
apparently that means it's invalid.

 

Same place you get your pulley bolt info.

 

for the same reason tires slowly lose air through the carcass. FWIW,
costco offers a nitrogen air fill. supposedly, the benefits are:

its dryer than regular air
its molecules are bigger than air molecules, reducing diffusion
less susceptible to expansion/contraction due to temp changes.

if anyone wants to dispute this, go right ahead

 

because for most people, its just not necessary. i do mine every 3
years, but i dont drive much and live in a semiarid climate. by the time
i do it, it comes out a tad darker (goldish) than the new stuff
(clear/straw colored)

and yes- ive seen my share of coffee-colored brake fluid.

 

a cheap shot not worthy of response, but you're getting one anyway.

let's examine the established facts:

1. bolts are roughly twice as hard to get off as put on - more than the
5-10% increase in torque anticipated by binding. even after one day of use.

2. the pulley wheel does lash - as evidenced by galling.

3. the greatest anticipated lash impulse is in the tightening direction.

4. honda felt there was sufficient need to change the pulley wheel
design in subsequent years to not just woodruffed, but woodruffed,
splined *and* loctited.

5. bolts are known to tighten in service depending on application.

what is not established is:

1. the extent to which any tightening rotation may occurr, if it does.

2. what else could account for a 100% increase in bolt torque in the
absence of serious corrosion.

saying "i don't believe it therefore it can't be true" really doesn't
cut it.