Had a problem with the 200tdi overheating (essentailly going to the top of the temp guage before it hits red) even with a fan fitted and heater on full, it made little difference, popped round a mechanically minded friend, he said we remove the thermostat, which we did, when i took the coolant level cap off, noticed a cream in the water, oh poo i think, head gasket gone, friend agrees and we then spend a cup of tea discussing options. Suddenly friend says, when we took the thermostat out the coolant was clear, and we didnt check the dipstick, so out we go, oil is 100% water free, we drain the header tank, which is full of crap, top up, and check the liquid again after 10 mins of running, clear and also temp guage is sitting low, spot on.