Not a lot of Water Coming out of Exhaust!

[Azul]

Running hot-worse under load, steam vapor in exhaust, contaminated coolant: equals blown head gasket or even small leak in head gasket. Get it checked by a mechanic. Each diesel is designed to run at a specific temperature and to have a certain amount of coolant flow to maintain that temperature which can be checked with the bucket method mentioned above. Too cool or too hot is bad. Coolant elbows gradually clog up when the salt water/rust/contaminants evaporate after running the engine. You should not have to be adding coolant that often. If you are a DIY you can rent a device at the auto parts store to check for a blown head gasket (basically a thingy that goes on the radiator cap and checks pressure etc. When I tried it on the Suburban the pressure went so high it launched the device like a Polaris missile as the leak over-pressurized the coolant system.(Disclaimer, I am not an engine mechanic but I found this escaped two mechanics when fixing my Suburban, but I now also have a new water pump and thermostat in addition to the head work...)