My 2007 Ram 1500 has 366,000 miles and still runs great. It uses oil and isn't quite as peppy as it once was but it is still going.
Last year I replaced the radiator because I spotted some crystallized coolant on some of the tubes at the edge of the tanks.
Since then, I still have to add water to the radiator. It doesn't leak when it is running. There is no steam coming from the exhaust pipes. I do notice some wetness under the truck in the morning, no more than a couple of ounces and not every day. I do see A/C condensation dripping sometimes.
Even with it on a car lift, I have never seen it drip from anywhere. There are a few small streaks on the engine block below the heads but again, it is never wet there.
I thought that I could have leaking head gaskets but with no steam from the exhaust and no difference in how the exhaust smells, I can't be confident that there is a leak there.
I guess a leak down test would be a good suggestion. Maybe a cooling system pressure test too.
Any other suggestions?