BG Universal Cooling System Cleaner PN 540 (1 Bottle) with Pocket Screwdriver Over time, rust and scale can build up in the cooling system. When deposits form on heat transfer surfaces, the engine loses the ability to effectively cool off. Buildup also restricts coolant flow, causing overheating and possible engine damage. Includes a Smilyeez pocket screwdriver. A strong cleaner that removes corrosion, tough residues, built-up scale, oil, and harsh mineral deposits. PN 540. 12 oz. (354 mL) bottle.