Yes, COOLANT is a Scrabble word!

Letter values in Scrabble US: C 3, O 1, O 1, L 1, A 1, N 1, T 1.

Is it a valid word?

COOLANT is a valid word in the official Scrabble dictionary (US), the UK Scrabble Dictionary and Words with Friends (ENABLE).

a fluid agent (gas or liquid) that produces cooling; especially one used to cool a system by transferring heat away from one part to another