I would question why you needed to deposit $210. That would be a red flag for me.
It sounds like they just sold you another radiator and will keep your money.
If they keep sending you more radiators, I would keep them and not send them back until you see your $210 back, or just sell the extra radiators that they ship you to get your $210 back.
If they were going to truely "warranty" the radiator, there is no need for the $210 "deposit".
And whose pocket is all the return shipping coming out of?