I have installed two radiators in a short period of time

What code was in the computer? Also, why was the radiator bad after such a short period of time?

I believe he said PO128....but I could be wrong. There had been problems with the "check engine" light coming off and on; however, it was on consistently when I took it in and never shut off the engine. The warranty on the first radiator was only a year. The replacement (possibly not original parts?) had a leak in the top near the cap at a weld or fold in the tank. We "split the cost" on the replacement radiator since it was so soon.

That code is means the engine coolant temp below regulating temp. Basically, it isn't warming up enough. The thermostat could be stuck open. Has it ever been replaced?

I bought the car in 2007. I don't have record that the thermostat has been replaced in the time I've owned it.

I bought the car in 2007. I have no record that the thermostat has been replaced in the time I've owned it.

That would be my next guess for the problem.

That would mean....? the faulty radiator CAUSES the thermostat to go bad? My original question was....at the time I had original problem with the radiator (or at anytime you replace a radiator), should you be thinking of replacing the thermostat at the same time because your upper hose is disconnected and fluids drained?

that would be the best time to change it. as far as the radiator causing the T-stat to go bad, no. However, a bad t-stat will cause overheating and may cause a radiator problem.