This component, known as the radiator coolant expansion tank , is a reinforced plastic container essential to the cooling system of JAC GS3, GS4, GS5, and GA4 vehicles. Its primary function is to manage the fluctuating coolant volume within the system. When the engine heats up, the coolant expands, and the tank receives this excess. As the engine cools, the tank draws the coolant back into the radiator, keeping the system completely sealed and free of air gaps . The tank also helps regulate cooling pressure via its cap.
If you notice a continuous decrease in coolant, or the presence of cracks, or discoloration of the plastic (yellowing and brittleness) in the old reservoir, this indicates damage to the reservoir and the possibility of leakage of coolant vapor, leading to a continuous shortage of water, and it should be replaced immediately.
⚠️ Important Notice: Please make sure the part matches your vehicle's chassis number before purchasing the product or after ordering.