I am adding fresh water cooling to my 3-cyl diesel because, when removing the existing exhaust manifold, I was dismayed by the amount of hard baked crud and rust flakes in it's water jacket. And in my case I could not physically access all the water channels in the engine block, so unseen accumulation is going on. I know you can use a laser thermometer to try to track down hot spots, but this can be a hit and miss affair.
(An engine reconditioner had a go at the exhaust manifold with his special chemical bath, but all the hardened stuff would not budge. Only a chisel seemed to do anything.)
You can't use anti-rust coolant
with raw water cooling and a periodic flush does not make a big difference, in my opinion. Still, as pointed out above, it's a cost-benefit equation for the owner.
To keep installation simple, you may consider:
1) A heat exchanger with built-in header tank, rather than separate. Both formats are available.
2) An electric
circulation pump, instead of an engine driven pump.
To ensure the heat exchanger is of adequate capacity (and not over sized), I contacted the heat exchanger manufacturer (Bowman, in my case) and his computerised simulation calculated the right size (note there is also variation in capacity between 1-way, 2-way and 3-way flows inside the same size exchanger). I had to supply the raw water pump
capacity and some engine specs.
Johnson Pumps manufacture an electric
circulation pump specific for engine coolant
circulation - no seals
(no maintenance) and magnetic drive. Johnson series CM10 and CM30, for which they claim MTBF of 2500 hours. Key point is the low current
draw - depending on model, max 2.5A - so even if the alternator
breaks down, your battery
bank could get you home. In some ways, this is similar to using an electric fuel pump
instead of an engine driven lift
By the way, I am still working on installing my setup, so if anyone here has any experience, suggestions or opinions regarding the good or bad of electric engine circulation pumps, I'd love to hear them.