I think this is the right name for it. Do your cars eat these things up? I'm on the second one and due for a third. It corrodes to the point that it starts leaking. This is the part on the passenger side by the firewall.
I've only replaced mine once because it was sticking in the closed position. I used the cheap Advance replacement with no issues. Maybe your coolant or water is corrosive or has excess sediment. Be sure to use distilled water with your coolant.