The Bleed Screw vents trapped air and prevents air pockets from forming. This ensures accurate temperature readings on the temperature sensor. Any closed system that uses fluid to operate in your vehicle, will also have a bleed screw to allow you to purge air from the system after a fluid change.
O-ring not included
Thread Info:
Ø 5.8 x 0.976 pitch (or 26 TPI) x 0.624 Length