If it is not leaking or overheating now an easy way to check it is to bring it up to temperature and take temp measurements with an IR gun in a grid pattern from the inlet to the outlet if it is clogged or has started to clog you will see colder readings where the clog is forming, for some reason they seem to clog in the center where the fan clutch is. Also you should see a drop in temperature of greater than 30 degrees F from inlet to outlet. When I checked my 23 year radiator there was a temperature difference of 50 degrees with no cold spots. As Richard said it is the inside that counts.