A valve cap includes an internally threaded cap; a sleeve including external threads and an internal passage; a flexible, spring biased insert including a conic top in the passage of the sleeve for blocking, and a transverse bottom groove; a hollow first cylinder including external threads threadedly secured to the cap, internal threads secured to the external threads of the sleeve, and an internal passage; a hollow second cylinder including external threads, lower internal threads, and an internal passage; a moveable, flexible insert member including a conic top, a stem, and a transverse bottom groove; and a hollow, cylindrical positioning member including an axial channel and external threads threadedly secured to the internal threads of the insert member. Groove of the insert member communicates with both the channel of the positioning member and inside of the second cylinder.