1999 3.0 4x4 heating/coolant problems

[JONNY246]

Last month I flushed coolant system out new antifreeze. About a week later no heat top hose barely warm no leaks also gurgling from the overflow.Once cover blew open coolant everywhere. was told could be air in system it was purged, no change. I decided to replace radiator (new) and thermostat and upper/lower hoses everything was fine back to normal. Last week temp gauge was erratic then finally didnt register and no heat top hose is barely warm including coolant, gauge decided to work on/off never went into the danger zone always stayed at 1/2 way mark . I recently changed plugs normal wear. oil looks fine doesnt look like baby shit no smell of coolant or noticeable leaks, no coolant comming from exhaust just normal condensation after sitting overnite no black soot in pipe or smoke no coolant inside on floor Truck runs fine has 179.000mi I have put a lot of work into this truck frame work,tires, suspension ect for a 1999 its in great shape It be greatly appreciated for any answers or advice on this issue. sorry for the long drawn out post Thanks