This is the plastic return pipe mounted on the back of the water pump and returns coolant from the pump to the expansion tank. The complete return pipe is two pieces and this is the upper portion coming out of the pump. The best way to access this pipe is with the intake manifold off, such as for a crankcase vent replacement.
This part is manufactured by an aftermarket supplier of European auto parts, including many engine and cooling components. While not carrying OEM status, this part follows the design of the original very closely but uses aluminum instead of the original plastic. An aftermarket part may even have the same TUV approval as its OEM counterpart. The brand may even be OEM to another manufacturer besides BMW. This aftermarket brand has a two year warranty - the same as Genuine BMW and OEM brands.
BMW Fitments:
3 Series
E46 (99-05) > 320i
E46 (99-05) > 323Ci
E46 (99-05) > 323i
E46 (99-05) > 325Ci
E46 (99-05) > 325i
E46 (99-05) > 328Ci
E46 (99-05) > 328i
E46 (99-05) > 330Ci
E46 (99-05) > 330i
5 Series
E39 (97-03) > 525i
E39 (97-03) > 528i 99-00
E39 (97-03) > 530i
Z Series
E36/7 / E36/8 Z3 (96-02) > Z3 2.5
E36/7 / E36/8 Z3 (96-02) > Z3 2.8 99-00
E36/7 / E36/8 Z3 (96-02) > Z3 3.0
Z Series
E85 / E86 Z4 (03-08) > Z4 2.5i M54
E85 / E86 Z4 (03-08) > Z4 3.0i M54