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I have been having some slow but excellent rust removal results by soaking in molasses and water. Does anyone have any reservations with using such a solution in the radiator and cooling system to remove rust deposits in the water jacket? Not while engine is running but in a stationary status?

Ingredients in molasses act as a "chelating" agent for certain metals, thus the "cleaning" action. Check "molasses" in Wikipedia for a good explanation of metal chelation. Simple oxalic acid available from paint and hardware stores does the same job, probably far better and faster. Oxalic acid was the major component in the heavy duty DuPont (and other brands) radiator and engine blockcleaners of some years back. The second component of those commercial radiator cleaners was a neutralizer (sodium carbonate) to be used after the oxalic acid treatment.

Typical of chemical reactions, the speed of reaction increases with increased temperature - oxalic acid cleaners like the DuPont product were used with the engine running to both get flow of the liquid, and to increase the rate of reaction.

This topic has come up quite a few times before, using the "search" function might be useful to you. Were it me, I'd forget the molasses and just go to the hardware store and get the real stuff.

Good advice, probably much faster too.

For smaller parts, Evaporust works 100 faster that molasses, and uses the same process. Also much like Molasses, it is not toxic to handle.