How to Replace the Radiator in a 2004 Audi A4

1. Turn off the Audi's engine and allow it to sit until the engine and radiator have both become cool. The radiator cannot be removed until the Audi has cooled because the coolant will be hot and may gush from the radiator.
2. Empty the radiator by opening the drain plug and draining the coolant into the bucket. Unhook the retaining clip with pliers, then unscrew the metal ring connecting the upper hose to the radiator and allow it to drain of any coolant. Repeat for the lower radiator hose. Check the condition of the O-rings that sit between the radiator hoses and the hose connectors on the radiator.
3. Remove the securing clips on either side of the top of the radiator, making sure to check the condition of the securing rubber. Detach the transmission oil cooler pipe as well as the transmission fluid cooler lines.
4. Lift the Audi's radiator out of the vehicle and set it aside, noting the position of the connectors.
5. Clean the radiator hoses inside and out, making sure to check for firmness, rips and/or tears. Check the condition of the retaining clips and check the radiator fan for any dirt or debris.
6. Replace the Audi radiator with the new one, noting the hose connectors and fan position. Reconnect the upper and lower hoses and replace the securing clips.
7. Pour the proper coolant/water mixture into the new radiator until it is full. Start the engine, and once the engine warms and circulates the coolant mixture, continue to fill the radiator until it reaches the top and stabilizes. Close the radiator cap.