It's starting to sound more like an electrical fault, since the comment in your previous post and I quote: "temperature gauge fluctuates all the time from four bars down to two is this normal".
I suggest that you inspect the connectors above the radiator for burnt / bad connection, as well as the power and earth connection points (battery terminals and earth strap).
How does the voltage look across the battery, with ignition on but not started? Then again the voltage reading, with the engine is running around 3,000 rpm? For a good charging system, you are looking for a reading in the region of 13 - 15 Volts at 2,500 - 5,000 rpm. Ensure that no accessories are drawing power when testing, as this could give a faulse reading.