As another user mentioned, you will need to be absolutely sure that fluid isnt leaking from any other location at all. If the hose burst caused the current cylinder to empty out, you will want to try a bench bleed, also as suggested, followed by rechecking all of the calipers for air. To check for fluid in the booster, you could try a wire hanger, or perhaps even your oil dipstick after wiping it off well, pull the vacuum hose off, and carefully stick that in to the bottom. If you pull it out and see any fluid, there's your answer, in which case I would replace it. You may be able to remove the retaining bolts to the booster and carefully pull in away a little bit to confirm a leak there, but if there's too much resistance, don't force it. If that's the case here, and a new master cylinder is needed, a bench bleed is necessary before installation. It may come with a bleeder kit and, if not, you may purchase one. Finally, rebleed the rest of the brake system to be thorough. If you haven't already flushed out the old fluid, now's your chance. You may as well do it. API is obviously aftermarket, which always runs a bit more of a risk of receiving a defect out of the box, but compared to other aftermarket brands, it's just as competent (in my humble opinion), though I would be careful bot to damage it during the bench bleed. A bench bleed is basically just connecting transparent tubes to where the two lines will connect and running them down into a container filled with some fluid. The whole process is A LOT easier with a vice. You'd fill the reservoir with fluid, depress the piston on the cylinder and watch the air bubbles work their way out. Pinch the lines tightly as the piston retracts and repeat this process until you see no more air. There are plenty of videos, online tutorials, etc. to assist you with this if you're more of a visual type of person. Lastly, if the new master cylinder doesn't come with the reservoir, obviously you'd move the old one to the new one. Good luck.
