Just going to say, diesel generators need special coolant, You can get from a variety of places, Freightliner or Cummins, or you can order it on amazon. I carry couple of gallons of it. Still getting air bubbles out of new engine. Check that one after every trip each evening when traveling. The PDF shows all the different types of coolant. The picture is the one my 6.7 engine is supposed to use. It can go in the generator, or the second one down from the top in the PDF can be used. I like to not have 6 different things for the same thing, so it gets the picture type. Once you get it filled up, between the marks, then check it once week until you know it's not losing fluid.
Also, please list your vehicle information in your signature file, as we on here would know how to help you better, knowing that. Have fun.