Changed the Master cylinder the pedal still goes to the floor

It sounds like you have an axle bearing that has gone bad and is causing an air gap between the brake rotor and brake pads. It will pump up but a short time later the brakes will be on the floor again.

Here is a guide so you can do some checking to confirm the problem.

https://www.2carpros.com/articles/how-to-replace-front-wheel-bearings-and-seals

and

https://www.2carpros.com/articles/bearing-hub-replacement

This can also happen when a caliper slide seizes. Check to make sure the calipers can move freely on the slides.

Here is a guide that shows you how to service the slides.

https://www.2carpros.com/articles/how-to-replace-front-brake-pads-and-rotors-fwd

If the brake hoses are leaking here is a video that will show you how to replace them.

https://youtu.be/xMS8Xy4Xz1U

Let me know what you find.

The booster typically wont make the brake pedal sink to the floor.

Here is a guide that can help you more i think.

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

You might have a bypassing master cylinder which is most common in some rare instances, it happens within the ABS unit.

Here is a guide to replace the master

https://www.2carpros.com/articles/how-to-replace-a-brake-master-cylinder

Please let us know what you find.

Cheers

Before you pull out tomorrow make sure you have a good pedal. If you were hearing a drag on one of the front bearings the noise can come and go.

On the brake lines make sure it isn't ballooning when you depress the brake pedal. I could be wrong, but those hoses go bad. They can cause the caliper to stick on of the fluid doesn't return due to internal damage in the hose.

Also, they can expand when you hit the brakes. Thus yo have a low pedal. Please double check the side that you heard the noise from.

This is sorta the way i bench bleed on the vehicle

https://www.2carpros.com/articles/how-to-bleed-or-flush-a-car-brake-system

this can be done on the vehicle (my preference) using two people, one pumping and one monitoring the master cylinder. i wrap string loops around the little hoses, and tie a knot, as to keep the tubes from blowing off of the plastic adapters.

i take it one step further, by squeezing the little hoses with my fingers (as if i were a check valve) the very slow pumping of the pedal will push the fluid into the reservoir, by my pinching, but will not allow it to suck air/fluid back into the mc (constantly an outward flow), as you will see happen in the beginning of this video....my way makes air purge faster, but if you did not tie the hoses to the adapters--they will blow loose (lots of adjectives will be used, and your eyes may burn!)

is this sorta what you did, off the vehicle?

this is the way i bleed (people often sorta do it wrong! on some newer stuff, other steps may be involved, the other guys may add that in, if needed, this way has always worked for me!)

i have tried the vacuum pump way, and also the line attached to a bleeder valve submerged in a cup of brake fluid........never satisfactory results for me!

this is the way i was taught

keep fluid in the reservoir at all times/ constantly checking!

start with furthest out wheel cylinder, from the master cylinder, working to the closest (rr, lr, rf, lf)

2 people, one pumping, other bleeding and refilling

1-man breaks bleeder loose (so it ain't so tight)-snugs it back yells, "pump it up"

2 man-pumps 6-8 times (yells "pumping") then holds pedal--yells, "holding" (never lets up, until told to)

1-man cracks bleeder...air/ fluid spurts out

2-man yell, "floor", just before the pedal, actually hits the floor

1-man tightens the bleeder....while it is still spurting out (not after it stops...or it will suck air back in).....then yells, "okay---pump it up"

after you get a rhythm going and your pumping man, is "trained", the lingo sorta turns into

1 man "ok!"

2 man "ok!"

and so on!

process starts over, until you are satisfied the air is purged out

you should have "drum brakes" already adjusted outward, before you do the bleeding procedure.

i have seen dummies break open the bleeders, and just start pumping away, then shut 'em......not good!

maybe you have done all of this--maybe you just didn't know---i figured i'd sling it out, just in case....many times we "assume" the other party is doing things correctly...then chase our tails, looking for non-existent, other possibilities
xbleeding

the medic

Glad you could get it fixed, that kind of problem can be tough. Please use 2CarPros anytime we are here to help

Cheers, Ken