Radiators

I have a 2007 ford explorer sport trac and have had 2 radiators put in and a water pump and the petcock glued shut on the most recent radiator. These are not ford oem radiators but just purchased from the local radiator parts dealer, not a cap type radiator. Both replacements have developed leaks at the bottom within a few weeks of replacement by the ford dealer. Is it possible to get 2 defective radiators, or is there too much pressure or something else that causes them to leak?

A radiator cap is the relief valve for too much pressure, I am guessing it has a radiator type cap on the fluid reservoir?

The installer might be doing a poor job putting stress on the radiator. A replacement rad should last a long time. I know it is a pain to keep going back to the dealer, but you have to let them figure it out. They are losing a lot of money on this too.