An air separator for low flow rate coolant systems which removes air from the liquid coolant thereof. The air separator is a closed canister having a bottom wall, a top wall at a gravitationally high location with respect to the bottom wall, and a sidewall sealingly therebetween. A coolant inlet is at the sidewall, a pump outlet is at the bottom wall and a coolant reservoir outlet is at the top wall. The coolant reservoir outlet is connected to a coolant reservoir gravitationally elevated with respect to the canister. A much larger cross-sectional area per unit length of the canister relative to the piping results in a coolant dwell time in the canister that encourages coolant air bubbles to migrate toward the coolant reservoir.