I'm using water in my XR6 atm, and it looks a bit cruddy.. Is coolant any better? My dad's a mechanic, and he's always used water..
really, are you BEGGING for your head gasket to sh*t itself???????
its a well known fact with the I6 that due to the IRON block and the ALLOY head if you dont use proper coolant you get electolysis happening which eats away the alloy and stuffs the head!!!
get the water out of the car asap and get some coolant in there! the stuff i use is called RCI 100, can be used from straight mix down to 33%, i use it straight. it says its good for 250,000km but i change it every year (along with gearbox oil/diff oil/brake fluid)
i havent been using it long enough to make a judgement on how good it is at stopping corrosion but it seems to be ok - its definately 1000000% better than tap water!!!
drain all the water out by taking of the bottom and top radiator hoses (turn the heater to 'hot' so the heater core empties as well) and totally remove the coolant reservior from the car, remove the sensor as others have said (you will prolly need a new rubber seal, mine tore when i pulled it out) clean it with a rag and use a hose on full blast to clean out the crap from inside the coolant reservior.
again put water hose into the top radiator hose to flush the radiator and then in the bottom rad hose to flush the engine.
drain as much tap water out as you can, refit everything and fill with appropriate amount/mix of coolant - when you buy it make sure you get a brand that says 'for alloy head engines'.