It is also called thermosyphon-cooling and in 1910 it was the first liquid cooling. It still lacked a number of the components which characterise todays cooling: a regulated fan, a thermostat, and a coolant reservoir. Accordingly, it was difficult for the engine to reach it's operating temperature quickly and to maintain it. The tight tolerances of today and the long service life were of course, not possible. The tall-built radiators stood in the way of the aerodynamics. For this reason the vehicles had the engines covered and attached fenders. The pontoon car-body, with the engine covering and the wheel-arches forming a unit, was not yet discovered.This kind of cooling had it's revival - indeed using a coolant - in the field of motorcycles. In this case there is no fan.
The warmer water rises between the cylinders. The highest temperature is reached in the cylinder head. The coolant reaches the radiator through a standpipe typical of the thermosyphon-cooling, where, slowly descending, it takes on a lower temperature. All that was regulated was the excess pressure. Only however, in one direction. With excess pressure, the coolant was bled off into the open air, which is why, when the coolant cooled down again, it had to be refilled.The fan was driven by the crankshaft. It's operating RPMs was dictated by the engine, regardless of whether the coolant was hot or cold. 05/10