Gasoline engines use a plastic reservoir, connected to the radiator by a hose. As the vehicle is driven, the coolant is heated and expands. The portion of the fluid displaced by this expansion flows from the radiator into the recovery bottle. When the vehicle is stopped and the coolant cools and contracts, vacuum draws the displaced coolant back into the radiator. This keeps the radiator full at all times, resulting in maximum cooling efficiency.
Keep the coolant level between the “HOT” and “COLD” marks on the recovery bottle. These marks are about one liter (one quart) apart. Use a 50/50 mixture of ethylene glycol anti-freeze and soft or distilled water.