Not trying to start a argument, but Im trying to think of any (popular,commercial) engines that dont have a oil cooler of some kind. Im almost postive, the Komastu PC200 I used to have, had a oil cooler on the side of the engine, the Cummins I have in my trucks have oil coolers, the Cat in my equipment has oil coolers, guess I cant think of any, but Im sure there are some
Let us know about the one you have, if you dont know what to look for, they are usually a 3-4" round thingee, that is mounted on the side of the engine. Some have water hoses going to it and some are mounted (bolted) to the block. There should be a way to drain the water out of it, somewhere on the bottom of the thingee
Good Luck