I know that you should replace the brake master

Hello, I'm Danny.

Here is the information you requested. You won't have to do a brake fluid flush but you will need to bleed the brakes after the repair. 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 bleed the system on your vehicle. Hope this helps and thanks for using 2CarPros.

On the brake reservoir where the clutch feed line goes is it supposed to be blocked or should it be open. The one I have is sealed no fluid comes out of it. Where does the clutch master get its fluid?

It gets its fluid from the brake master but not from the place where you think. Here is a guide that shows the replacement (below) the unit is self bleeding.

Check out the diagrams (below).

Let us know what happens and please upload pictures or videos of the problem.

Cheers, Ken