2006 Ford Explorer radiator issue

The radiator on the vehicle needs to be replaced as there apparently is a large crack and it is leaking antifreeze. I have a Powertrain limited warranty thru 8/12 or 75K miles. My mechanic says approximate $500 repair. He suggested I take it back to dealer as repair may be under warranty and his radiator supplier told him there was a recall with this. Ford dealer initially told me they thought it was covered under warranty. The dealership called to tell me it was not covered under warranty and the vehicle was half way apart. The cost to replace being $700. Also said they had no knowledge of recall. My mechanic has been great over the past couple years; the dealership has been difficult since purchase of the vehicle.

Can you tell me if there is a recall on this or if it should be covered under the warranty?