When the engine heats up, the coolant expands and releases excess pressure. As the engine cools, the fluid flows back into the radiator to maintain proper operation. 603-054 Engine Coolant Expansion Reservoir Tank with Cap Compatible with Chevy Silverado 1500 2500 Tahoe, GMC Sierra 1500 Yukon, Cadillac Escalade 2007-2013 Replace# 22870828 15075118.
