Received the Temp Too Low...P0128 SES code. So, am replacing thermostat housing. As I have 78K on the car was thinking I may want to do the water pump while in there. Can someone tell me if the 06 ZHP has the newer composite impellers or are they the older plastic type that were known to be a weak point. If I replace it I'll go with the metal bladed type. Live in AZ. Thanks.