I'm quite new to bikes. I have a Schrader valve bike with deflated wheels. When I try to pump it up. I take off the protective cap, then there is a valve secured down by a nut (there is another nut securing it to the actual wheel) I then put the pump onto the bit of valve poking up and lock it in. I can then pump it completely with about 5 pushes of the pump. Once it is complete I unlock the bike pump off of the valve, at that moment all the air rushes out immediately (10 seconds) even if I put the protective cap on. What does this mean??
From these three, which one you have?
Check if the inner part (valve) is properly installed (tight enough). If is and still loose air — you need to change the valve or the inner tube, the problem is with one of them.
You need to unlock the valve before pumping, or you will pump air only into you pumps' hose. After pumping don't forget to lock the valve back.
Woods (Dunlop) valve
Very old system. Check inner parts (steel needle and rubber tube) for damages, rubber tube can degrade flexibility with years → air loss.