Coolant Expansion Tank Cap, OEM - E36, E46, 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 is an OEM expansion tank cap manufactured by Behr - an original supplier to BMW for many cooling system components. As an OEM it meets all of BMW's original design, fitment, and performance requirements and is TUV approved. OEM parts are the best alternative to more expensive Original BMW parts because they are virtually identical without the inflated price tag. This part has a two year warranty.