brake pedal.

[prosantos]

Brake pedal goes all the way down, need to pump a few times for it to go back up.
What is causing this issue???

[notoptoy]

Most likely dried seals on the Master cylinder, other culprits, air in lines, or leaking wheel cylinder. Look for brake fluid inside the firewall at the brake pedal.

[C.Costine]

Brake pedal goes all the way down, need to pump a few times for it to go back up.
What is causing this issue???

Classic air in the lines or cylinders. A few pumps will temporarily compress the air so that the brakes will work. Try bleeding them to see if you can get some air out. As to why there is air in the system it can be a few different reasons. As you go to each wheel cylinder to try bleeding air, look for leaks, as well as above the brake pedal as notoptoy said, and take a good look at all three of the rubber lines. Plan on the bleeders being rusted unless you have maintained them, so you will want to apply penetrating oil a week before you plan to try to bleed them. Brake fluid tends to absorb moisture from the air so the brakes should be bled annually since the moisture tends to make its way to the wheel cylinders. Moisture tends to also get under the rubber dust boots of the front wheel cylinders. It's not difficult to lift the retaining ring and lift the edge of each boot and inject some WD-40 to push the moisture out.