[90 Accord] Master or Wheel cylinders going?

Hi there,
1990 Accord EX, 189k, well maintained. Recently the brake pedal
will fade (close) to the floor: about 1/3-1/2" of play left once it's
down there. PA winter, was about 45F today when it happened(so not
abnormally hot). Only happens on slow braking. If, after I have
stopped, I hold me ebrake and pump the brake pedal, the stiffness
returns within 1-1/2 pumps. Hard braking is OK, just slow that give me
trouble. I have read here that this is most likely the master
cylinder(internal leak), because there is no loss in fluid-it is solid.
How can I tell it is the master cylinder and not a rear wheel
cylinder(rear drum, front disc)?

Remanned from AdvanceAuto is ~$50. How hard are these to rebuild(I'm
fairly mechanically inclined, just never done one before). Also do I
need to bench bleed the new master before installing it(I had to on my
'92 Nissan).

Thanks folks!
-Jamie

 

wrote in

Pull a wheel (and drum as required). Leaks will be blindingly obvious. If a
disc leak is bad enough, fluid will be flung around on the inner face of
the tire.

If a leak is due to a rotted line, you'll get staining on your driveway.
And maybe a little pee-stream underneath when you stomp the pedal.

Does the pedal eventually go to the floor if you hold the pedal long
enough?

Are you _sure_ there's no fluid level drop...?

 

If it's a wheel cylinder, there would be leakage at the wheel, and fluid
loss. If your fluid level hasn't changed, it's the master cylinder.
All master cylinders are suppose to be bench bled, but I prefer not to. The
risk is that you may have a bad one and not know it until it's in the car...
But if the two bolts are easy to get to I bolt it in and fill the
reservoir. I plug both )Or all) ports with fingers and have someone gently
pump the pedal until I get pressure and fluid from a port. Then I attach
that line and repeat until all lines are in place. Done correctly, you won't
have but a small bit of air (or even none).

 

Steve/Tegger, I'll just respond to you both at once.

Yeah I've pulled all the wheels, and everything is dry as ever...
usually brake fluid will stain suspension parts and is pretty
noticable... that being said, the fluid in the resovour is really dark,
perhaps it's time for a flush and change anyways. Are Honda's really as
picky about their fluid's as my brother leads on(he's been a mech. at
honda for a while), or can I get away with plain 'old DOT3(minus
silicon)?

I didn't thoroughly test every situation, but it seemed to continue to
go to the floor as long as I was slow about my pedal pressure, and
'stopped' at a light in traffic. When I returned and parked in my
driveway, still running, I was really stabbing the brake pedal, but it
remained solid/stiff(trying to induce or force a leak...) As mentioned
above, there may be a *slight* drop in fluid, but since my resovour is
so dirty it might be hard to notice. Certainly nothing noticable.

Just checked out the FAQ: wish I had know about it earlier!

I'm not sure I follow you: is the risk the inconvenience of bench
bleeding it first only to find out it is bad anyways? What's are some
tell-tale signs that a MC is bad-from-the-box? Not too long ago my
friend put a NAPA remanned on a neon that was no good. I'm just
wondering if it's worth the hassle.

Thanks for your responses! I'll be sure to post back w/any updates.

 

plain old DOT3 or 4 will work. 5 is the silicone stuff. supposedly,
honda *brake* fluid isnt all that great. maybe due to the time it spends
sitting on the shelves at the honda dealerships?

 

Mike,
Just to clarify, you can get any 'grade' brake fluid w/silicon.
Good point about the brake fluid.

 

Have a 91 Accord and had this same problem but in the summer when it got
very hot outside, this was corrected with a new master cylinder. Have also
had a leaking wheel cylinder but the pedal stays hard as normal.

 

Sounds like the MC except they usually exhibit this behavior in warm
weather, not cold. Yours may be more gone than you think, especially
with that many miles on it.

Not much to lose if you can find a rebuild kit.

 

it's master cylinder then.

don't use dot 5 unless you replace every seal in the system, including
the proportioning valve. even then, it's not recommended unless used in
seriously wet conditions as it has a lower boiling point.

fluid gets darker when it absorbs moisture. when the system is bad
enough for the rubbers to start deteriorating, the detritus washes back
into the chamber blackening the fluid.

bench bleeding for a honda is not critical - they bleed easily. [vital
for some other cars tho]. assume the new cylinder is good.

to bleed, a fudge is to replace the cylinder & connect the brake lines,
but not tighten fully. you can then bleed in situ only tightening the
lines after they stop bubbling without having to bleed the whole system,
but that is NOT text book. /correct/ procedure is to bleed the whole
system per tegger's faq's. again, do NOT attempt this shortcut unless
you know what you're doing.

very important: have a gently running hose handy when bleeding. wash
any spillage with plenty of water. if you get it on the paint work, DO
NOT WIPE - wash only. even if it looks like paint's coming off, just
wash & keep gently washing for a few minutes. then go back into the
house for an hour. when you come back out, the paint will look like
there was never a problem. unlike if you stay there & get tempted to
touch it "just to see" if it was ok. trust me on that one. when
washing, be careful not to slosh water into/onto the fluid reservoir -
contaminates the fluid.

 

If I understand you correctly, you're letting the air bubble out from the
threads on the flares at the master cylinder, and once you get pure fluid
squirting out, you tighten the flares then bleed at the wheels?

 

yes. quick & dirty, but it works.