Which one is better/more durable? The car comes with plastic, which in my case (Coolant leak after timing belt replacement) is damaged. I only find aluminum thermostat housings. Why is that? Does anybody know the part number for the plastic thermostat housing?

 

I go with the Aluminum on the thermo and Waterpump. stock is Plastic

 

I got the aluminum one. The sales operator told me that the plastic has been discontinued.