drmini in aust wrote:
Many European cars (Fiat, Alfa etc anyway) have the thermo switch in the bottom tank of the radiator. Theory here is that only if insufficient airflow, will the bottom tank get hot. Worked fine on my Fiat...

Yea the later Rover Mini rads have the thermo switch inbuilt into the bottom part of the rad right?
From reading other peoples experiences on this and other forums one thing seems to come up most often - those who just slapped their fans on without a shroud and without any mods didn't get the full benefits and couldnt rely on just the thermo fan. Even brickworx helpful as usual, only recomends the original straight bolt on fans off Rover and Jap minis he brings in, as helper fans with continued reliance on the mechanical fan.
In those cases, however, where the setups were more complex the thermo fans seem to work fine - the standard mini fan sits inside a shroud approx 5 mm from the radiator, so when it pushes air, it wont go anywhere but through the rad. When you slap a fan in the wheel arch however, without a shroud etc - it sits about 100mm from the radiator so its effect is muffled plus it can suck air from between the rad and the cowl and from behind it all of which reduce its efficiency dramaticaly.
Now I'm sure I've seen traditional side mount rads from injected Rovers, with a thermo fan infront of the radiator and no other fans. So I'm thinking if one could mount a fan hanging inside a shroud infront of the rad, or a very powerful unit inside the wheel arch but again inside a shroud and with a direct sealed passage to the rad (ie with any other gaps apart from the radiator gills, closed) then one would get an efficient setup. I think the cruch here is primarily this absence of air leaks and maybe the distance between the fan and the rad.