What's the tank which covered by the coolant cap called?
 

What's the tank which covered by the coolant cap called? not the A.S.T /////// if i want to order one from Mazda, what should i call it, and should i replace one because i have my 7 for 9 years already

thank you

you talking about the radiator overflow bottle? It has a line going from the pressure cap to the top of the tank?

thanks