VegasVet said: of course over flow tank is never full,
Why do you say "of course"? Your coolant reservoir should be about one third full, and the radiator should be 100% full with a cool engine. As the coolant in your engine heats up, it expands, and the excess will flow into the reservoir.. As the engine cools off, the coolant will contract, and the coolant in the reservoir will be drawn back into the radiator, thus keeping your radiator 100% full. This presumes you have a good radiator cap!
The reservoir is not an "overflow tank". If the reservoir becomes "full", something is wrong. If the radiator does not stay 100% full, something is wrong.
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