The idea that it goes to the floor is usually related to a faulty master cylinder. Take a look through this link:
https://www.2carpros.com/articles/brake-pedal-goes-to-the-floor
If there are no leaks, no air in the system, and everything is sealed, this is my first suspect.
Keep in mind, when you start the engine, you get assist to the brakes which makes it much easier to press. Try this: With the engine off, hold pressure on the brake pedal. See if it slowly goes to the floor.
Let me know.
Joe
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Saturday, September 18th, 2021 AT 9:10 PM