Models 520i, 523i, 528i
Removal
Remove the expansion tank cap.
Caution: When the engine is hot, place a thick cloth around the expansion tank cap before opening it to avoid scalding from hot liquid or steam. Risk of accident! Open the cap only when the coolant temperature is below +90°C.
Unscrew the air bleed plug "1" and bolts "2".
Remove the top part and pull the tank out with an upward movement.
Installation
Replace the "arrow" sealing rings.
Insert the expansion tank, tighten the upper part fastening and the air bleed plug.
Fill the cooling system and bleed it, see section "Maintenance work".
Warm up the engine and check all connections for leaks.