If there are no leaks, the master cylinder is likely the problem. Take a look at this link:
https://www.2carpros.com/articles/brake-pedal-goes-to-the-floor
If you feel it mirrors what you experience, here is a link that explains in general how it's done:
https://www.2carpros.com/articles/how-to-replace-a-brake-master-cylinder
Because you are replacing the master cylinder, chances are you will need to perform an automated bleed on the ABS module. That will require a scan tool that can communicate with the ABS module.
The attachments below are the directions specific to your vehicle. You will need to manually bleed the system. I attached the directions for that as well.
One other thing, make sure to bench bleed the new master cylinder as explained in the link I attached.
Let me know how things turn out for you or if you have other questions.
Take care,
Joe
See pics below.
Images (Click to make bigger)
Friday, April 1st, 2022 AT 1:51 PM