I have a range rover 2000 ;4.0se . I have had intermittent overheating issues. I can drive for 20 miles and then the temp gauge spikes to the red. I will turn the engine off,30 seconds later turn it back on and it will be fine for a few minutes and then spike again. It can go up ,stay in the red,and then go back immediately to normal. I have replaced the thermostat, and just last week the radiator. Its still overheating. I have been very careful to turn the engine off and the engine seems fine. Any suggestions?????????