Not U600 specific but in general there is one drain plug on the water pump housing and may be one at the lower part of the cylinder. One usually lifts the front so the radiator is well above the engine..say 6-8"s. I pull the cap, and drain plugs and I pull the lower radiator hose and drain the recovery tank. Reassemble and while the front is up start refilling the system with 50/50 mix of a quality coolant...say Prestone or Peek. At about half full I add about 4 tablespoons of water pump lubricant then top to about a half a finger-depth down from the top. Start it and let it run adding to keep the level the same as needed. Then when it warms-up enough for the thermostat to open it will show a much greater flow rate and heat. Give it about 30 seconds to work any air out then top off to the very top and install the cap with NO air gap. Then fill the recovery bottle to the full mark..plus a little extra for good measure. Drop the front and that's it. Well check for leaks. Use anti-seize or a good pipe dope on the plugs and DON'T over tighten...they break easy.