Petrol engines: Open the air bleed valve 1 on the thermostat housing. On the 518i model, the valve is located directly under the ignition distributor.
Models 518i, 520i, 525i only: Additionally, open the air bleed valve "arrow" on the top of the radiator next to the expansion tank.
Diesel engine 524td: Open the air release valve "arrow" on the thermostat housing.
Fill the coolant through the opening in the expansion tank until the tank is full and coolant flows out through the air bleed valves. The illustration shows the expansion tank on the 530i, 535i and diesel engines.
On the 518i, 525i and 525i models, the expansion tank is located directly below the radiator.
Close the air release valve on the thermostat housing.
Start the engine and push the gas pedal to rev up to 2500 rpm. The air remaining in the system causes the coolant level to drop to approximately the MAX mark on the expansion tank.
During the heating process, add liquid as needed and then close the lid.
Check the cooling system for leaks, especially at the hose connections.