Reduced Braking Power

[RusT]

Hi Everyone, 

I need your help in diagnosing a brake issue in my car. Since last Thursday or so, the braking power in my car has been reduced and I need to press the pedal more than I used to to get the brakes work fully. 

I also saw similar threads posted by the members some time ago such as:

My car is a Vitz (SCP90) and the recently following repairs were done to the braking system:
- Bleed and replace brake fluid (Around 6 months ago).

- Replaced both front pads and rear shoes (Akebono, around 4 months ago) and drums were also resurfaced.

Observed the following as well:

- No any warning lights on the dash.

- Reduced brake power is consistent, however if the pedal is pumped twice, the brakes will grab as it used to earlier.

- No reduction in brake fluid.

All the repairs mentioned above were done at the same garage that I usually do my repairs and when I took the car to them yesterday they told that it could be an issue with the master cylinder. They said they'll have to inspect further before confirming the exact issue (will be taking in the car tomorrow).

I want to know what to look out for, as if it is the master cylinder, can it be rebuilt using a washer kit or does it have to be replaced?

Any other areas I need to check for any leaks or other signs.


Really appreciate your thoughts on this.

[iRage]

Well...without actually giving it a proper diagnosis there really isn't much to say other than what your garage guy said...there could be something wrong with the master pump.

Depending on how the pedal feels and what you mean braking power is reduced (does it take a longer distance to stop or the pedal goes in deeper despite the pedal feeling hard and tight) it could even be the booster having pressurization issues.

You might also want to check if there are any fluid leaks inside the drums. You might not notice any significant reduction in brake fluid in the fluid tank itself but there might be a small seep somewhere. Such seeps can be well hidden in drums as it gets covered (I am assuming that front and the brake lines running to the calipers and drums are nice and dry). Also it could be that one of the shoes are misaligned and not working properly (can happen with pads but its far more obvious that something is wrong). Any noises ? Over heating of the brakes ? Burning smell ?

[RusT]

Hi @iRage

Thanks for the input.

It's a combination of both actually, the pedal goes in deeper and takes a longer distance to stop. The pedal is feeling of kind of mushy, or spongy. Sorry for the choice of words, but that's how it feels.

And no noises or heating. No burning smell as well.

 

I'll update after proper inspection 

[RusT]

Issue was with the master cylinder, removed and checked inside the bore, there was some noticeable rust (may be due to no timely replace of bf by the previous owner) therefore a seal kit wasn't enough and I had to replace the master cylinder pump. After replacing, bled the brakes completely and refilled with new brake fluid.

No leaks inside the drums as well.

Brakes are now working great, no loss of stopping power or pedal feeling spongy.