C 1500 Yukon 2WD V8-5.3L VIN Z Flex Fuel (2003)
Coolant Reservoir: Description and Operation
Surge Tank
The surge tank is a plastic tank with a threaded pressure cap. The tank is mounted at a point higher than all other coolant passages. The surge tank
provides an air space in the cooling system that allows the coolant to expand and contract. The surge tank provides a coolant fill point and a central air
bleed location.
During vehicle use, the coolant heats and expands. The increased coolant volume flows into the surge tank. As the coolant circulates, any air is allowed
to bubble out. Coolant without air bubbles absorbs heat much better than coolant with bubbles.