Brake pedal slowly sinks to the floor

SUBHI

MEMBER
2007 SUBARU IMPREZA
1.5L
4 CYL
2WD
MANUAL
105,000 MILES

I have big problem with brake system. Slowly sinking brake pedal, if I push the pedal hard it will not sink and every thing is fine, but if I little bit put my feet on the pedal it will slowly sink to the floor. I replaced the master pump and bleed the lines still same problem. No warning light no brake and no ABS light.
Noticed when the pedal in the floor there is a brake feel and the car can stop.
If you know the reason please tell me the solution. Thanks

3 Replies

JACOBANDNICKOLAS

MECHANIC
109,867 POSTS

Hi and thanks for using 2CarPros.com.

It sounds like you have a bad master cylinder. If the pistons in the master cylinder are bad, they can allow fluid to slowly leak past them resulting in the pedal going to the floor. Take a look through this link.

https://www.2carpros.com/articles/brake-pedal-goes-to-the-floor

You say you replaced the master pump. Are you referring to the master cylinder?

Let me know,
Joe

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Thursday, October 18th, 2018 AT 7:40 PM

SUBHI

MEMBER
2 POSTS

Yes the master cylinder.
But still same problem.
And no external leak.
The problem appear just when I step on the pedal and need more pressing it sink to the floor this sink can stop the car with poor break action.
But if do not step on the pedal and press it suddenly and hard it will not sink and brake action very good.

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Friday, October 19th, 2018 AT 3:05 AM

JACOBANDNICKOLAS

MECHANIC
109,867 POSTS

Hi again.

Honestly, if there are no leaks and the new master cylinder does the same thing, check to make sure none of the rubber brake hoses are expanding when this happens. You will need a helper to press the brakes while you watch what happens.

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Friday, October 19th, 2018 AT 7:33 PM