Coolant Expansion Tank Kit, Rein - X3/X4 28i, 35i M40i

New coolant expansion reservoir tank, level sensor, and cap for F25 X3 and F26 X4, including 28i, 28d, 35i, and M40i.

The cap is not just to seal the coolant expansion tank - it regulates and maintains the pressure in the cooling system. 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 is very common for this expansion tank to get brittle and crack over time, leaking coolant, causing overheating, and potentially stranding you on the side of the road. The constant hot/cold temperatures and positive pressure of the cooling system stress the plastic until eventually a crack develops. If you are replacing any other part of the cooling system in the X3/X4, we suggest inspecting and replacing this tank as a preventative measure.

This is an expansion tank kit manufactured by Rein (CRP) Automotive - 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.