Hey! Are IC engine cooling systems positive pressure (pumping from radiator bottom to radiator top)?

A water cooled thermocycle IC engine will be cooled both ways. The cooler water in the radiator becomes heavier and will move to the bottom of radiator and engine.

Once inside the engine the coolant receives heat form friction and combustion and becomes lighter and rises to the top of the engine pushing the warm coolant into the radiator.

Add a mechanical pump and the hot water is drawn from the engine block into the radiator using positive pressure delivered into the radiator top. That would include negative pressure in the engine block being drawn into the pump and positive pressure delivered back into the radiator.

In any closed cycle pump system there will be positive pressure and negative pressures.

Now there are open pressure systems where the coolant will be pumped from a lower pool into the hot engine and then be forced higher above the engine to gravity return from a wet wind screen. That would be an example of a totally positive pressure system.

A modern fresh water boat would be an example of a positive pressure system drawing fresh water and using it under positive pressure to force it threw the hot engine to cool it and return it out side the engine.

Thanks, Fred.

To use quasi-popular vernacular, I find myself some-wont awed.

So, if I understand correctly:

The boat motor has the advantage of inexhaustible coolant reservoir so needs not to manage differential pressure dynamics as is the case in non-open systems. On the other hand, the pictured, unidirectional, variable speed coolant pump, augmented by coolant gravity feed from radiator bottom hose, essentially serves to neutralize pressure differences (at first startup only) within the engine block by pumping (respectively drawing and forcing) coolant from points of greater pressure to points of lesser pressure—essentially circulating water coolant in block bottom by drawing it out from one port and forcing it out through the other (because the weight of radiator tank coolant “reservoir” prevents back flow from the block/pump) …plus sending relatively cooler water to engine block top through the heater coil circuit, until…

…until, by temperature driven convection and density drop, the block becomes “t’stat uncapped,” permitting ejected/return hot coolant flow to radiator to displace cooler coolant drawn by pump from radiator bottom.

As for open versus closed systems, it seems that by removing the radiator cap that prevents boiling loss and by unblocking the t’stat flow path, one would have converted the IC engine cooling system from closed to open, but…a system soon to fail fatally due to size limitation of the coolant reservoir.

Best answer and then some.