Ongoing over-heating problems with 2006 Defender 110 300tdi....

Hi,

I have a Defender 110, 300TDi which I bought in March 2006. It over heated 500 miles after buying it and so had the head skimmed, new gasket and it worked for another 1,000 miles until the head bolts shot out of the head, taking all the threads with them. So then I replaced the head, gaskets and bolts. Then it ran for a few months maybe 2,000 miles after which it overheated again. That time I had the block rectified, new cylinders, new head, rockers etc., valves, gaskets, tubes and thermostat.
Four weeks ago it overheated again after driving only 40 miles, the heating inside was only blowing cold and it shot up to red from one second to the next. I had it towed back home and then off to the mechanics again. This time I had the head checked which was OK, new gasket and bolts. Once I arrived home I let the motor cool and checked the coolant which was up to the brim in the expansion tank, so I think it was about to overheat again.... the heater inside was working though.

I wondered if anyone has any tips for me.... I also have changed the alternator, viscous fan and a few other bits and pieces. The fan on the inside of the radiator revolves freely by hand... is this normal or should it be stiff to move? Should I replace the radiator? some blockage? Or could it just be a thermostat problem? or something else!??

I'd of had a new rad on it long ago, also thermostat and water pump then find a better mechanic

My defender 2.5na overheated when I bought it the needle always in the red. Over time I changed the water pump, flushed out the radiator, changed the thermostat, new sensor to the block and even changed the the temp gauge on the dash all had no effect. Basically I gave up and just drove it with the gauge in the red for a couple of years. I then found out that the thermostats come in different opening temps the one that was in it I think was 90 something degrees I swapped it for one that was a lower temp 72 degrees I think and it cured it. Not sure if this is the same for a 300TDI but worth checking out.