brake pedal goes to floor - brake master cylinder?

Hello, I'm Danny.

Here is the information you requested. Here are a few tutorials for you to view on how to replace a brake master cylinder and how to bleed the system after the repair has been made:

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

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

Since you are installing a new brake master cylinder it would be best to bench bleed the unit before installation to remove air from the new unit prior to installation on the vehicle. Here is a YouTube tutorial from our site showing how to do so:

https://youtu.be/WDxvEQrMkBg

I've attached picture steps below on how to replace the brake master cylinder and how to bleed the brakes on your truck. Hope this helps and thanks for using 2CarPros.