Brake pedal sounds like an air pump and goes to the floor

[Chris90]

I have a MY23 3.3L Stinger.

Recently, when braking from a very low speed, I heard faint rubbing sounds from somewhere on the front left (outside of the cabin) (this sound has not occurred anymore). After that the brake pedal has been strange.

The brake pedal started to sound like a manual air pump. The brake pedal can also be pressed all the way to the floor - not with the first press but gradually while maintaining pressure.

I took it to the dealership and the outcome was that "nothing is wrong". They also let me try the brake pedal of a used 2021 Stinger and while the sounds were the same they were much fainter. On the 2021 Stinger the brake pedal went almost to the floor, but not as much as mine. But I know for sure my Stinger's brake pedal was silent before this.

Not sure what to think. All car repair help videos on YouTube say that if the brake pedal sounds like an air pump or goes to the floor then something is about to fail.

I uploaded some videos, the engine is running in all 3:

 

[Snicklefritz]

If you pump the brake pedal does that firm it up for a while? You've got a failure somewhere letting air into the brake lines. Bleed the brakes, check fluid level, check fittings to make sure none of the lines have come loose, etc. Ima no mechanic. But over the years I've experienced what you shared a couple of times, where the brake pedal made that whooshing sound, and if you just push it and hold that pressure the pedal will travel clear to the floor. When the brakes do that, the only way to safely slow and stop is to pump the brakes, don't just press and hold or you'll lose brake pressure. Get this fixed post haste. Your dealership are morons.

 

[Chris90]

If you pump the brake pedal does that firm it up for a while? You've got a failure somewhere letting air into the brake lines. Bleed the brakes, check fluid level, check fittings to make sure none of the lines have come loose, etc. Ima no mechanic. But over the years I've experienced what you shared a couple of times, where the brake pedal made that whooshing sound, and if you just push it and hold that pressure the pedal will travel clear to the floor. When the brakes do that, the only way to safely slow and stop is to pump the brakes, don't just press and hold or you'll lose brake pressure. Get this fixed post haste. Your dealership are morons.

The pedal does get firmer when pressing it multiple times in a row (engine on). But then once it has not been pressed for a while it gets soft again. In contrast, sometimes when moving from gas pedal to brake pedal quickly, it is a bit firmer.

Going to take it to the dealership again soon. Might need to get a 2nd opinion from a mechanic if dealership doesn't investigate further.

In these ~2 weeks since the problem started the pedal has got even softer. Sometimes I can press it to the floor in 1 go with moderate force, as opposed to taking pauses while keeping pressure.

Can some others also describe their brake pedal travel distance?

 

[Snicklefritz]

Can some others also describe their brake pedal travel distance?

My brake pedals in both Stingers feel the same, very firm with little travel. It would alarm me greatly if my brakes were soft and the pedal traveled a lot. If the pedal bottomed out on the floor, I would not drive the car. I can't understand why you are letting this take so long. Please don't do that!