Surge Tank (6.6L Diesel Engine)

WARNING: This page is about a different car, the 2010 GMC Sierra, 2010 GMC Cab & Chassis Sierra, 2010 Chevrolet Silverado, and 2010 Chevrolet Cab & Chassis Silverado. However, it is still accessible from the selected car via links, so may be relevant.

This surge tank is actually two chambers connected together, (a surge tank and an overflow bottle). The front chamber (closest to the engine) is the surge tank and is the highest point of the coolant system. It uses a threaded pressure cap, similar to the one used on a radiator or engine fill system. The rear chamber (closest to the fender) is the overflow bottle. This is the air space in the cooling system where the coolant can expand into and contract from.

During vehicle use, the coolant heats and expands. The increased coolant volume can in some conditions push past the pressure cap and through a channel into the overflow bottle. As the coolant circulates, air is allowed to bubble out. This air is then transferred to the overflow bottle, through the surge tank cap, where it returns to the atmosphere. Coolant without air bubbles absorbs heat much better than coolant with bubbles. When the engine cools, the coolant, without air bubbles, contracts back into the surge tank from the bottom of the overflow bottle.