radiator resevoir keeps slowly going low, no white smoke out of the exhaust pipe, all the spark plugs are the same color and one is not cleaner than any other, no spark plugs are the color of the antifreeze, no leaks or fluid on the ground under the vehicle
Very likely to be the water pump on these - its visible under the timing belt covers. Look for crusty deposits around that area. Failing that it could be your heater matrix that has failed, but there would normally be quite a strong smell inside the car.
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