Coolant Expansion Tank Cap - E36, E46, E34, E39, E38, X3, X5, Z3, Z4

While your BMW cooling system may be considered very reliable, it's all depending on this coolant reservoir cap. This cap is not just to seal the coolant expansion tank - it regulates and maintains the pressure in the cooling system (2.0 bar). A failed cap can lower the pressure inside the system and lead to an overheating situation. Replacement of the cap is recommended every three years to ensure optimum cooling efficiency and performance. It's a simple and inexpensive preventative maintenance step.

BMW has had many different part numbers for this radiator cap over the years. This part number replaces BMW numbers 17117639022, 17111742231, 17111712669, 17111712492, and 17110152374.

This part is manufactured by an aftermarket supplier of European auto parts, including many cooling components. While not carrying OEM status, this part follows the design of the original very closely and uses similar materials. An aftermarket part may even have the same TUV approval as its OEM counterpart. This aftermarket brand has a two year warranty - the same as Genuine BMW and OEM brands.