How Do I Replace the Radiator on a 2001 BMW 325Ci?

1. Disconnect the electrical plug that goes to the MAF sensor on the air filter housing by pulling it off. Remove the two 10 mm mounting bolts that hold the air box in place. Loosen the large clamp that fastens the air intake hose to the manifold. Remove the air box and the intake hose.
2. Disconnect the electrical connections located on the passenger’s side of the fan shroud. Loosen the large fan bolt (in the middle of the fan) with a large adjustable crescent wrench by turning it clockwise to loosen it. It is reverse threaded. If you cannot loosen the fan belt without the water pump turning, you will need a special tool to hold the water pump while you loosen the bolt, which is available at the BMW dealer or online. Remove the fan and shroud from the engine bay once the fan bolt is loosened.
3. Loosen the front wheel’s lug nuts. Lift the vehicle with a floor jack and lower it onto jack stands. Place a container under the radiator. Loosen the radiator drain plug and let the coolant drain into the container. Move the container under the engine block drain plug, located under the intake manifold. Remove the drain plug bolt and let the coolant drain. Reinstall the drain plugs.
4. Remove the hoses from the radiator expansion tank. Remove the expansion tank by pulling straight up. It may take some effort, but it will come out. Disconnect the electrical connections on the bottom of the tank. Set the expansion tank aside.
5. Loosen the hose clamps that hold the lower radiator hose in place. Remove the radiator hose. You may need to push on the edge of the hose with a screwdriver to get it to slide off. Pull up on the quick-disconnect that holds the transmission cooler in place (on cars with an automatic transmission). Pull the transmission cooler away from the radiator and let it hang on the lines that go to it.
6. Remove the Torx screws on either end of the radiator that hold it in place. Angle the top of the radiator away from the front of the car and pull it straight up and away from the car.
7. Remove the transmission thermostat from the old radiator on cars with automatics and install it on the new radiator with the same Torx screws, or install a new transmission thermostat.
8. Clean the area by the bottom of the radiator mounts with a wire brush or similar so it's free of dirt and debris. Slide the bottom of the new radiator down so the wedges on the bottom of the radiator are lined up with the grooves where the radiator installs.
9. Pull the radiator towards the front of the car until it seats. Reinstall the Torx screws that hold it in place. Reinstall the transmission cooler (on automatic cars) and reconnect the quick-disconnect fitting. Plug the electrical connections back into the radiator.
10. Reconnect the lower radiator hose and tighten the hose clamp. Reinstall the expansion tank by sliding it back into the engine bay. Reconnect the hoses to the tank. Reinstall the air box and the air intake hose. Fill the cooling system with coolant.