91 Honda losing brake fluid

I have a 91 Honda Accord, great car. However recently I have been
losing brake fluid. About one a week I have to fill the reservoir.
Now here is the kicker. I have checked and had it checked by multiple
mechanics and there are no leaks in the system that I (or they) can
see. And there is nothing on the garage floor after parking there.
Very wierd. Anyone seen anything like this or know of any other
explanation? Any help is appreciated.

 

Chances are it isn't gonna leak out when sitting, but under pressure.
There's obviously a leak somewhere. Try pumping like crazy while
sitting, then trace and check the lines, master cylinder, and
calipers/wheel cylinders again. Could be leaking in a place where it
doesn't drip right away. Take the wheels off, of course, and maybe even
remove the calipers to get a closer look at the piston seals.

 

Just DON'T pump like crazy with the calipers removed, or you could eject
the pistons!

 

probably leaking into the vacuum servo or inside the car from the master
cylinder - not usual that it happens like that, but it can. all other
leaks should be obvious. check /all/ brake lines & hoses as well as
calipers, drums, etc.

 

My car had a similar problem. Turned out to be a loose brake hose on the
right rear drum. The fluid was dripping ever so slightly from the hose
and running down the inside of the rim. Very difficult to notice.

 

any way it could be sucked thru the vac port on the brake booster, and
burned by the engine?

 

Probably? ;-) I haven't seen that myself, but it sounds reasonable. My
experience is far from complete.

 

the servo would have to be mostly full to do that - the vacuum port is
at the top on the 91!

 

HIGHLY unlikely it's leaking into the booster. Two O-rings seal that end up
awfully well. And it cannot leak into the car at all unless it first fills
up the booster then perforates the diaphragm, then fills up the other side
as well.

I think the OP has a holed line or it's leaking out of a caliper or into a
drum (if so equipped). Drums must be /removed/ to check.

Have helper step HARD and steadily on pedal, and watch underneath for
drips. If leak is mild, wind will sweep fluid away at speed. Best to have
car on hoist & have strong light. Hold pedal for five minutes or more.

Does car have ABS?

Additional slightly possible source of leaks is base of reservoir. If clamp
is loose or body is corroded, fluid can seep past.

Does car have other leaks that could obscure leaking brake fluid?

 

i've seen it. not on a honda, but i have seen it.

 

Some MC designs (especially older unboosted designs) did not seal the rear
of the plunger well. Those can leak into the car.

The Honda MCs I've seen have all had a rear plug with two O-rings. Leakage
from that is VERY rare. And even then it would have to fill up both sides
of the booster before leaking into the car. The booster could hold an awful
lot of fluid.


He's got a leak somewhere else, I'm convinced. Just nobody's finding it.

 

My money is on: fluid leaking into the vacuum booster.

 

wrote in

Basically, that's completely impossible. The rear chamber has no pressure
in it.
http://www.tegger.com/hondafaq/mastercylinderreplace/howworks.html

 

not so - it's extremely common for the bore seal to go. look around a
junk yard and you'll see boosters with leakage evidence [missing paint]
all the time. the question is whether it will leak /into/ the booster,
and while the honda booster has a drain where the cylinder is mounted to
mitigate this, it can still happen. it depends on how greased up the
original seal was and whether the drain is plugged.

doesn't need it. in fact, seals don't leak much under pressure because
they get pressed against the cylinder wall. it's seepage from when the
seals are relaxed that is the biggest problem.

 

Thanks for the info I hve pumped and pumped but see no leaks. I am
going to pull the wheels next and see what I can see

 

No idea on being sucked thru the vac port not sure what that is even.

 

How can you check the booster?

 

I will remove the drums and look again at everything. Yes it has ABS.
No other leaks.