I just had my dealer do the upgrade to the cover (plastic) on the coolant pump (under the engine). My question is... I looked at the new cover next to the cover they took off. They looked exactly the same. The part numbers were different by 2 numbers. New was 420812342 Old was 420812340. They both are plastic. Does anyone know if the new plastic cover is better than the old and if it will expand at the same rate as the aluminum of then engine. Why didn't they upgrade this piece with an aluminum cover? any input would be appreciated!