The factory water manifold on most 24 valve, six cylinder vehicles are made of plastic. Unfortunately plastic will not handle the heat, or over torquing of the mounting bolts. We have discovered that even the new plastic manifolds from BMW can be warped by as much as 1/16". Water leaks resulting in overheating has claimed many of these engines due to the failure of the original plastic component. We have now reproduced this item in a more stable, low-pressure cast aluminum. If the original unit on your vehicle is not leaking at this time we strongly recommend replacing it regardless. Inspecting the original piece may reveal a slight coolant stain. In this case we recommend replacing the unit at once. We recommend also replacing the profile gasket at the same time.