Brake pedal still sinks to the floor after master cylinder replacement
A sinking brake pedal usually indicates lingering air trapped inside the hydraulic lines or an internal leak within the anti-lock braking system (ABS) control module that standard bleeding cannot clear. When pressure bypasses the system valves, it forces you to pump the pedal multiple times to generate stopping power, preventing the vehicle from achieving immediate, firm braking.
What people tried
Every workaround mentioned in the threads below. We haven’t tested any of them — and nobody here is claiming they worked.
Found another way around this?
Share your steps and trade-offs so fellow engineers don't have to reinvent the wheel. No account required.
- 1replacing the brake master cylinderDid this help you?
- 2bleeding the brakesDid this help you?
- 3pressing the brake pedal multiple times to build pressureDid this help you?
- 4Changing brake pads and shoesDid this help you?
- 5Checking calipers and wheel cylinders for leaks or failureDid this help you?
- 6Flushing brake fluidDid this help you?
- 7Checking or replacing the master cylinderDid this help you?
- 8Bleeding air out of the brake linesDid this help you?
- 9Disabling traction or stability control to test for changesDid this help you?
- 10Bleeding all four calipers starting from the one farthest from the reservoirDid this help you?
- 11Using a vacuum brake bleed kitDid this help you?
- 12Getting an ABS brake bleed service performedDid this help you?
- 13Using reverse bleeding or pressure bleeding methodsDid this help you?
- 14filling up brake fluid and pumping the brakesDid this help you?
In their words
Unedited, grouped by where they were said, most upvoted first within each place, each linked to the thread it came from.
“i replaced the caliper where the brake pad fell off, and both front rotors and brake pads. when i first tried bleeding the brakes, i left the spout open and just pumped the brakes but then learned that that doesn’t work because it fills the brakes back up with air.”source ↗
“does anyone know where i should go from here? i don’t have enough money for a mechanic and would like to do this myself if possible.”source ↗
“Hello, my brake pedal goes all the way to the floor when braking so I decided to switch out the brake master cylinder and bleed the brakes as well. I’m still having the same issue. Brakes go all the way to the floor.”source ↗
“Occasionally the brake pedal would work but I would need to press it 2-4 times to give it pressure and would work normally only for that moment.”source ↗
“When I am coming to a stop, the car before coming to a complete stop, it feels like the brake loses tension for half a second and the pedal goes down a bit & then it stops.”source ↗
“Woke up this morning to a spongy brake pedal that was sinking all the way down to the floor, was still able to use but it obviously took more effort.”source ↗
“Made it to autozone and filled it up with brake fluid and attempted to pump my brakes.”source ↗
“Still depresses down to the floor but it does feel a bit better than it did.”source ↗
Where this came up
People with this problem also raised
- 10Why is my brake pedal mushy after a service?
- 6Why does the clutch pedal stay down and feel soft?
- 8Why do brakes still fail after replacing calipers and bleeding?
- 8Why is my brake caliper piston so hard to compress?
- 2Faint brake grinding noise after an alignment
- 5Why does my steering feel loose and clunking?