2010 Honda Civic had catalytic converter and radiator replaced. What type of Problem would cause this?

2010 Honda Civic had catalytic converter and radiator replaced. What type of Problem would cause this?

Added (1). I'm looking at buying a used car, I found a 2010 Honda Civic w/ 66,000 miles. It had the catalytic converter and radiator replaced. What type of mechanical problem would cause this?

Radiators can suffer from physical damage like an accident, or from salt air corroding them when parked near the ocean too much.

I once had a catalytic converter fail because I lived on a hill; when I started down the hill when the engine was still cold in the morning it would run too rich, or it would run too lean and backfire. The inside of many catalytic converters are ceramic with platinum wires. Backfire will sometimes break the ceramic inside. Also, if the car is not kept turned up properly it can backfire and ruin the converter. Some will say I'm wrong, but the ceramic does break, and it did on mine. After the ceramic breaks, the converter will have pieces rattling around loose and make noise. Also, a bad catalytic converter will not pass an emissions test.