i'd suggest a themostat is necessary every time.
if you have ever washed dishes you know how long it takes that water to cool to a temperature that doesn't scald you hands.
the reverse is true as well. if it takes a long time to cool it takes a reasonably long time to warm up .... both actions driven by different temperature differences and different proceses so not comparable, but you get what i'm drving at.
same can be said of a furnace based, home heating system, with pumped water radiators in each room. the exit valve from each radiator should be set to 1/4 turn or less from being closed, Not full open. To slow the water flow in the radiator down so that it sheds 12-15 degrees as it traverses the radiator. with both open fully the water goes through too fast and is 1-2 degrees cooler and thats all....
takes you from a "hot to touch" radiator in a cold house, to a radiator where you can feel the heat coming off it from 2 foot away, a warmer house, just by adding that restriction.
a large mass of water traveling slow enough to dump its heat into the brass or aluminium of the radiator works best
Anything you can do to keep the water moving in bulk, but relativly slowly, improves cooling, hence the resriction provided by the thermostat is necessary and the cooling system has nice fat pipes.
The thermostat provides something for the pump to push againts, which reduces the chance of cavitation and the pump/block damage by errosion it causes... (everyone thinks standard pump impellors rust...they do. but that only half the story).
and it keeps what is the the block and heads long enough to pick up heat...and what is in the radiator ....in the radiator long enough to shed it
which is even more important when the ambient temperature is higher
without it you get a very hot engine and a very hot radiator but neither is shifting heat into the coolant and out again to the air flow in an efficient way. all indications to an observer is that the cooling system is working well... its not. the radiator is hot but the vast majority of heat energy created is still stuck in the motor. the cap vents or you blow off a pipe, so you buy a massive aluminium radiator.....
suggest water/blue coolant is still the best.... its specific heat capacity is appropriate for the design of the system. which matched radiator size and pump impellor rpm to the heat generated by the motor at the specific load/rpm
a race car with a standard pump should actually run a pump/pulley gearing that slows down the pump.... seems counter intuative, but the system was designed for a redline of 5000. if the car spends its time at 7000 change the gearing to make the pump think its 4000- 5000 and reduce parasitic loss at the same time. race cars don't tend to idle in traffic jams
sorry gone off on one i know little about electric pumps, but you should run a thermostat in my opinion.... might save you having to buy a huge radiator and carrying around another few lbs of coolant to fill it.
Dave
