Hi,
I have 2002 V6 TDI Passat 4 motion TDI Tiptronic. It has a mileage of 160,000km about 10,000kms ago the engine coolant temperature started to drop below 90oC (it has been rock steady for 3years at 90) to about 85oC particularly when I was driving it down hills and on flat motorways. The temperatrure reads down to 80oC when coasting down long hills.

The timing belt was changed at 125,000 with the water pump but not the thermostat.

Questions:
1. Is it ok to run it with this problem until the next timing belt change 250,000 and then change the thermostat with the water pump.
2. Could it be another fault ie: the coolant fan staying on permantley or something else.

I am worried that the engine is running to cold and will not burn the fuel efficiently and may cause the turbo and injectors to fail due to incorrect burning of the fuel.

Thanks.
PJCL