Brake booster or Master cylinder going out?

[snukkums]

So I had an almost poop my pants moment on the way to work this morning. I had to brake a kinda hard for a yellow light and my brake pedal just kept going almost to the floor but at a consistent but less pressure than usual. After I had stopped I was able to basically press the pedal to the floor and it barely held me at a stop. Once I pumped it, it was mostly acting like normal just slightly more travel than normal. This happened luckily two lights away from work and was able to stop with no issues to get into my parking spot. I didn't immediately notice any fluid but I will check again before I leave.

Is this my master cylinder or brake booster going out? I don't think it felt air was in the lines since from what I remember the pedal will have an inconsistent feel it was air.

Edit: also I have a tpms sensor that is either bad or needs to be resynced.

Thank you!

 

[MikeinNH67]

In my area, that would often mean a rusted brake line is leaking, generally going to the rear brakes. Do you hear the brake pump running?

 

[snukkums]

I forgot to respon,d my couple month old AutoZone duralast brake caliper was leaking fluid.

 

[RetroJunkie]

how's the reservoir look? When this happened to me, mine was still full and was the master cylinder.. Also a quick inspection behind each wheel and even your driveway can give clues to a leak or not.

That aside, the pedal behavior you describe is exactly what happened when my M/S was done..

 

[rdruss]

Something getting weird with my brakes. The "red" brake light has come on a couple of times and the brakes feel spongey. Fluid level is good and fluid is only a year or so old. If I turn the key on and press brake pedal can hear the pump come on, but I don't hear it run excessively when out driving. Any ideas? Thanks!

 

[SocalSam]

Brakes pulling to one side? That could be caliper seal.

If not pulling, could be air in the lines or in the valve block. If in the block, have assistant or toolbox press brake pedal and then crack the metal lines.

If bleed does not fix, then it could be master cylinder seal. Disable pump either at the connector or via fuse. On a flat driveway with plenty of space, try braking with pump disabled. Brake pedal should be rock hard. If spongy, then suspect master cylinder. Be careful with this test. Braking action will be diminished.