Did a brake flush damage my master cylinder?
 

I recently had the brake fluid flushed on my '95 Honda Civic (80k
miles). A week later I noticed my brake pedal would slowly sink to the
floor while I was waiting at red lights. I took the car back to the
service center (part of a large national chain), and they correctly
determined that the master cylinder was the culprit. They denied,
however, that the brake flush had anything to do with the master
cylinder failure. (To hear the office manager tell it, you would think
the master cylinder was totally unrelated to the brakes.)

Now I'm not a mechanic, but I'm having a hard time believing that the
master cylinder just happened to give out when it did.

Earlier today I read that the seals on the master cylinder can be
damaged if the mechanic drains the brake fluid by depressing the brake
pedal all the way to the floor, and that a professional shop should use
other equipment to get the job done.

Am I wrong for assuming the mechanic took some shortcut (or just didn't
know better) and ended up damaging the master cylinder?
Or is this the kind of thing where, even if done correctly, the master
cylinder still can get damaged?

(I did read a comment that it's not uncommon to have to replace the
master cylinder after having your brakes worked on.)

The new master cylinder cost $260. If the mechanic was negligent, I
don't want to have to pay for it. If, however, it's just part of owning
a ten year old car, I'll suck it up.

What do you think?

- Kevin

) scribbled:

> Am I wrong for assuming the mechanic took some shortcut (or just didn't
> know better) and ended up damaging the master cylinder?

Probable.

> Or is this the kind of thing where, even if done correctly, the master
> cylinder still can get damaged?
> (I did read a comment that it's not uncommon to have to replace the
> master cylinder after having your brakes worked on.)

Happened to me recently. Replaced *ALL* calipers with new ones,
new rotors all the way around, new pads, new lines. Bled the
brakes - never could get a solid pedal.

Turned out, once I replaced the master, all was fine. And there
wasnt anything wrong with the system in the first place - I had
a nice solid pedal. It was time to do a brake job anyway, and I
figured with 190k miles, I might as well redo the whole system
(sans the master).

--
remove MYSHOES to email

>
> Earlier today I read that the seals on the master cylinder can be
> damaged if the mechanic drains the brake fluid by depressing the brake
> pedal all the way to the floor, and that a professional shop should use
> other equipment to get the job done.


Nope, not true. Mechanics have bled brakes for decades by applying
pressure,
loosening the cocks, and allowing bubbles and old brake fluid to exit.

You dont have to use fancy equipment, although it makes the job faster,
though
not necessarily better. Doesnt hurt anything.

On 6 Jul 2005 16:39:50 -0700, wrote:

>>
>Now I'm not a mechanic, but I'm having a hard time believing that the
>master cylinder just happened to give out when it did.


You would most likely be correct. The master cylinder tends to get
rust and gunk in the bore because you only push the pedal so far down.
When the brakes are bled if you push the pedal to the floor then the
seals in the master cylinder get torn up by the rough surface. Once
the seals are damaged fluid leaks by them internally in the master
cylinder causing your pedal to drop.

Most pros use a litte device that forces the brake fluid through the
system using its own pressure so that they never have to touch the
pedal and don't risk this happening. I don't know if you will have
any luck getting the shop to admit that though. I sure wouldn't have
them replace the master cylinder if they don't know any more about
brakes than this.

Steve B.

On Wed, 6 Jul 2005 wrote:

> I recently had the brake fluid flushed on my '95 Honda Civic (80k
> miles).

Good for you for thinking to do so. Most people never give their brake
fluid a thought.

> A week later I noticed my brake pedal would slowly sink to the
> floor while I was waiting at red lights. I took the car back to the
> service center (part of a large national chain)

Stop going to large national chains. It is almost always a poor idea.

> they correctly determined that the master cylinder was the culprit. They
> denied, however, that the brake flush had anything to do with the master
> cylinder failure.

Horse****.

> (To hear the office manager tell it, you would think the master cylinder
> was totally unrelated to the brakes.)

See above re national chains.

> Earlier today I read that the seals on the master cylinder can be
> damaged if the mechanic drains the brake fluid by depressing the brake
> pedal all the way to the floor, and that a professional shop should use
> other equipment to get the job done.

That is exactly right. Scunge, corrosion and rust build up in the area of
the cylinder where the piston never normally travels. If the bleeders are
opened and the pedal pressed to the floor, it forces the piston and its
seals into this area of rough crud and corrosion, which can tear up the
seals and abrade the piston, failing the master cylinder in short order. A
pressure bleeder is the correct equipment with which to do a brake fluid
flush.

> The new master cylinder cost $260. If the mechanic was negligent, I
> don't want to have to pay for it. If, however, it's just part of owning
> a ten year old car, I'll suck it up. What do you think?

It's not part of owning a 10-year-old car, necessarily, but you'll never
prove it. You're probably stuck for the $260, but turn it into a valuable
lesson: Find a real mechanic! Every town has independent Honda
specialists.

Steve B. wrote:
> On 6 Jul 2005 16:39:50 -0700, wrote:
>
>
>>Now I'm not a mechanic, but I'm having a hard time believing that the
>>master cylinder just happened to give out when it did.
>
>
>
> You would most likely be correct. The master cylinder tends to get
> rust and gunk in the bore because you only push the pedal so far down.
> When the brakes are bled if you push the pedal to the floor then the
> seals in the master cylinder get torn up by the rough surface. Once
> the seals are damaged fluid leaks by them internally in the master
> cylinder causing your pedal to drop.
>
> Most pros use a litte device that forces the brake fluid through the
> system using its own pressure so that they never have to touch the
> pedal and don't risk this happening. I don't know if you will have
> any luck getting the shop to admit that though. I sure wouldn't have
> them replace the master cylinder if they don't know any more about
> brakes than this.
>
> Steve B.

Personally I'm kind of of the opinion that it should be replaced anyway.
I have repeatedly advised not to "pump bleed" older cars but I just
feel better replacing the MC anyway.

nate

--
replace "fly" with "com" to reply.
http://home.comcast.net/~njnagel

The manager is a big fat liar because lots of do-it-yourself articles
refer to the very same problem. You may find something about it at
www.popularmechanics.com (I once read about it in the printed
magazine's automotive Q&A column) or www.motor.com (back issues of
Motor magazine). I ruined Dad's master cylinder the first time I ever
flushed brakes, and as a result I've never pushed the pedal too far
while flushing, and I've never ruined a master cylinder since then.

You should file a complaint at www.bbb.org and any regulatory or
consumer agencies and also do a credit card chargeback for the work
already done.

> wrote in message
. ..
> >
> > Earlier today I read that the seals on the master cylinder can be
> > damaged if the mechanic drains the brake fluid by depressing the brake
> > pedal all the way to the floor, and that a professional shop should use
> > other equipment to get the job done.
>
>
> Nope, not true. Mechanics have bled brakes for decades by applying
> pressure,
> loosening the cocks, and allowing bubbles and old brake fluid to exit.
>
> You dont have to use fancy equipment, although it makes the job faster,
> though
> not necessarily better. Doesnt hurt anything.
>
>

> wrote in message
. ..
> >
> > Earlier today I read that the seals on the master cylinder can be
> > damaged if the mechanic drains the brake fluid by depressing the brake
> > pedal all the way to the floor, and that a professional shop should use
> > other equipment to get the job done.
>
>
> Nope, not true. Mechanics have bled brakes for decades by applying
> pressure,
> loosening the cocks, and allowing bubbles and old brake fluid to exit.
>
> You dont have to use fancy equipment, although it makes the job faster,
> though
> not necessarily better. Doesnt hurt anything.

Ive seen this done, and done it myself for years, but have never damaged a
master cylinder. Still, the logic is there that it could happen, and I have
to
retract my statement above. Just because I always got away with it doesnt
mean it doesnt happen.

wrote:
> > wrote in message
> . ..
> > >
> > > Earlier today I read that the seals on the master cylinder can be
> > > damaged if the mechanic drains the brake fluid by depressing the brake
> > > pedal all the way to the floor, and that a professional shop should use
> > > other equipment to get the job done.
> >
> >
> > Nope, not true. Mechanics have bled brakes for decades by applying
> > pressure,
> > loosening the cocks, and allowing bubbles and old brake fluid to exit.
> >
> > You dont have to use fancy equipment, although it makes the job faster,
> > though
> > not necessarily better. Doesnt hurt anything.
>
> Ive seen this done, and done it myself for years, but have never damaged a
> master cylinder. Still, the logic is there that it could happen, and I have
> to
> retract my statement above. Just because I always got away with it doesnt
> mean it doesnt happen.

My experiences are exactly opposite, I've only done brake work on
exactly one car over the years where I a) didn't replace the master
cylinder up front and b) didn't end up replacing the master cylinder
after it failed shortly thereafter. Of course, Murphy is always
hanging out with me...

nate