Answer:
Even if you throw it away, it still comes back.
What object has keys that open no locks, space but no room, and you can enter but not go in?
I'm the son of water but when I return to water I die. Who am I?
Without coolant, you'll have some trouble with this.
They can be long or short; they can be grown or bought; they can be painted or left bare; they can be round or square.
What is always coming but never arrives?