Water boils at 100c at the coast and less at altitude even when it is not under pressure. The Safestop Temperature Switch switched at above those temperatures. It naturally follows that the cooling system must be sealed for the Safestop switch to work

Safestop creates a controlled stop - not a breakdown. If the driver was permitted to crank the Starter Motor when there was a fault he could burn out the Starter Motor or flatten the batteries. This will turn the stop into an expensive breakdown.

The Safestop water level system is intelligent. It also monitors the quality of the water. If there is oil in the water the unit will activate. This may assist with and early warning that there might be an engine fault - Head gasket etc.

The Safestop system does a self check each time that the ignition is turned on. As the engine is not running there is no Oil Pressure. Thus the oil light remains on until the engine has started and the oil pressure is sufficient to pass the oil pressure switch point and switch the light off.