Leak in Master Cylinder

I took my 89 Civic car to two mech. They told me my car is leaking
from m/c. They told me to replace right away. I talked about brake
line leaking. They jacked it up and showed me my brake line are all
fine. He said just change the m/c. My simply thought is m/c is so
small I'm thinking I can changed by myself. I believe
the leak is between m/c and power boost. is there a seal or
gasket place bewteen m/c and power boost. all I can do is just
unscrew two bolts holding a m/c from power boost. do you think
I just replace the seal or gasket rather than replace the whole
master cylinder?

 

wrote in

Sure can. But make sure you get that new pushrod adjusted correctly. It you
don't, the brakes will not work properly, and may even lock on as you
drive.

It can also be difficult to bleed all the air out of the new master
cylinder without bench-bleeding it, so you'd get a spongy pedal.

And you have to get all the hydraulic connections undone without stripping
the nuts, which can be a _lot_ harder than it sounds, even with the correct
type of wrench.

There is an almost 100% chance at this point that the seals INSIDE the
master cylinder are bad, and those likely due to corrosion in the bore.

The sort of questions you're asking are those of someone who does not
really understand his braking system. Uness you want to spend a week or so
fussing with this to get everything right, I'd suggest serious Googling,
library reading, or just pay the mechanics for their knowledge and
experience.

 

I advise you to have a mechanic do it for you unless you have a friend
that can help you that has done this type of repair.

 

id recommend this, at least until youve done other brake work first,
like pads, flushes, replacing wheel cylinders and calipers on your own.
ive only needed one m/c done, on my old vw vert, and i paid the $150 or
so to have it done.

 

That's bad news if it's leaking out near the booster.

You can probably replace the MC yourself but you must have the repair
manual. There's lots you can screw up without following the procedures
and knowing the specifications. The consequences would be severe.

 

Great post. I agree with you. I have seen some posts in recent months
related to people that have air in the brake lines. It causes all sorts of
problems. While changing a master cylinder-if you don't follow the proper
procedures--you can end up with air in the brake lines. It reminds me of
an old poster I seen in a garage owned by a mechanic. It said PAY ME A
LITTLE NOW OR A LOT LATER. It's a variation of PAY ME NOW OR PAY ME LATER.

 

No. The fluid is leaking out of the MC into the booster. You need to
keep the fluid in the MC, not just keep it from leaking out of the booster
after it leaks out of the MC. It is a good idea to get this done ASAP
since your braking system is an important safety feature.

 

Alex Rodriguez wrote:

^^^
nice understatement!

 

And you would be amazed how many people are lackadaisical about their
brakes.

A few years ago my neighbor across the street came over to tell me the
brake pedal on her Cavalier went to the floor whenever she drove. This had
been happening for "a few days".

On inspection, the master cylinder was empty, and the pedal did indeed go
to the floor. Refilling the M/C resulted in a waterfall of fluid running
down the inside of the tire when the pedal was depressed. The caliper
piston was very rusty, the rust levering a big gap between the piston and
the hydraulic seal. Wish I'd got pictures.

I advised her to not drive the car any longer until the car was fixed,
advice she...thankfully...heeded.

Here's a fun one:
http://www.tegger.com/hondafaq/rustybrakes/aerostar_new-old_rotors.jpg
This person came to me complaining of "grinding" from her Aerostar's
brakes. How long had this been happening? "Oh, it just started..." Yeah,
right.
Yes, the inner rotor face is totally gone. It takes a while to work the
piston back into the caliper when it's sticking out that far.

 

shoulda kept driving it, and it woulda turned from a vented rotor to a
solid one!

 

Ah yes, an unvented rotor...suddenly, it's the '70s again!

LOL

 

This isn't really a difficult job to do (~about an hr or less). I'd
recommend you get a Haynes manual or the factory manual if this is
your first time doing this. Just have someone on hand to assist you
with purging air out of the system (at the MC after install and at
each end of the brake lines) and have a flair wrench to loosen the
screws for the brake lines at the MC.


Nick

 

for most people nick, that would be sound advice. however, the o.p. is
well known here and regularly demonstrates a frightening inability to
grasp basic mechanics. google this forum for some of their posts. the
/only/ safe advice here is to take the vehicle to someone that knows
what they're doing.

 

Great post--I agree with you.