Engine Cooling problem
1999 Rover 4 Series 4 cyl Two Wheel Drive Manual 94000 miles

engine overheating and fans cutting in. replaced radiator as i suspected blockage but this did not help. decided to replace thermostat and this did not work either. did a few other checks and noticed that the top half of radiator was very hot and bottom was cold. i then checked all hoses and found that they all warm except bottom radiator hose which is cold. i dont think its the head gaskett as its not using any water and there is no gunge around oil cap etc. decided to remove thermostat and drive without it in and everything going ok. everyhing pointing to thermostat so i cant understand why when i replaced it, it did not solve problem. checked thermostat i purchased in boiling water and its working ok. any ideas?