Ongoing Issues with Mazda 6 Master Cylinder

Over the last five years I’ve had to replace the Master Cylinder multiple times, which I’m to understand from the mechanics is “extremely unlucky”, however I feel there is another underlying issues. This includes twice when the replacement part was defective right out of the box.

I believe that there is a fundamental parts problem that is not being addressed by Mazda and I am comfortable saying that as I have not heard one comment or statement from Gallo Mazda about contacting the manufacturer or Mazda Corporate about addressing this issue.

Is anyone else having this same, repeat issue with their Mazda 6 and if so how were you able to get it resolved?

I have some questions.

What are the symptoms?

Where are you acquiring these master cylinders from?
If they’re not from a Mazda dealer then why do you consider it a fundamental parts problem not being addressed by Mazda?

How did you determine the part was bad right out of the box and what was the “bad” part?

In almost every case of repeated part replacements the real cause is a misdiagnosis or installation problem. I’m not going to state definitively that’s the case; only that the odds of getting 4, 5, or 6 bad parts in a row are so remote that it’s hard to buy into it.

This is a brake master cylinder I presume. Well, it is possible you are indeed just unlucky. I’ve gotten a defective one before, right out of the box. But you seem to be getting a lot of them. I should mention the defective one I had was an aftermarket version, not an OEM version. If you seem to have more problem with OEM version, try an aftermarket. Or if you have problems with aftermarket MC’s, visa versa. Usually OEM versions are the more reliable.

hmmm … and maybe the problem isn’t the replacement MC at all. well, another idea, your brake fluid is dirty. Dirty brake fluid can damage a good MC. Ask your shop to first flush out the old brake fluid, before installing a new MC. Another idea, if your shop does brake fluid flushing and/or bleeding using the “push on the pedal” method, than can damage a MC that is still good, but has been in service for a while. The piston gets pushed beyond its normal range and small spurs can develop over time, which will rip the seals during the bleeding operation. This is best avoided by the shop using a pressure bleeding machine.

Finally, make sure your shop bench bleeds the new cylinder before installing it. If that’s not done, its possible for it to act like it isn’t working, but the problem was actually that there’s air somewhere remaining b/c it wasn’t bench bled first.

Based on the previous post in 2011 there seems to be a dissatisfaction with the performance/reaction of the brake pedal.

From the complaint it would seem that the master cylinder is failing, however even brake systems with a simple vacuum booster are not simple anymore. Advanced brake systems are equipped with a stroke sensor and a pressure sensor on the booster. These systems don’t react or behave like old brake systems.

This is a brake system description from the owners manual;

Brake Assist
During emergency braking situations
when it is necessary to depress the brake
pedal with greater force, the brake assist
system provides braking assistance, thus
enhancing braking performance.
When the brake pedal is depressed hard or
depressed more quickly, the brakes apply
more firmly.

When the brake pedal is depressed hard or
depressed more quickly, the pedal will feel
softer but the brakes will apply more firmly.
This is a normal effect of the brake assist
operation and does not indicate an
(Without DSC vehicles)
When the brake pedal is depressed hard or
depressed more quickly, a clicking noise
from the brake booster may be heard. This
is a normal effect of the brake assist and
does not indicate an abnormality.

Brake assist is not the same as ABS functions. When there is a rapid application of the brake pedal the system may view this as a panic stop and modify the brake application for a more rapid stop. This may seem unusual in performance but the goal is to stop the vehicle as quickly as possible.

This may not be what you are experiencing but shows that these systems are not so simple to diagnose. One can’t quickly assume the master cylinder is faulty as suggested is the previous thread.

Take the car on a quiet street and perform a few panic stops and see if this is the reaction you are experiencing.