I recently purchased Engine Guard unit for 2 vehicles. First install was to my 2008 Mini Cooper S. They have aluminium block as well as aluminium head, and are designed to run hot.
I also fitted new silicon coolant hoses. I used 2 sensors, one fitted to the head/inlet manifold at the water pump end. The other was attached to the opposite end of the head at the thermostat housing and radiator hose end.
I drove the car intentionally hard to force maximum temperature. Just as I was changing down gears for my driveway, the Engine Guard alarm went off showing a warning for both sensors. Luckily I was 50 metres from my driveway.
One off the new stainless hose clamps had failed and the lower radiator hose had blown off.
I was extremely impressed with the warning and on checking under the bonnet noted the alarm was so quick to alert me that the radiator hadn’t even had a chance to empty fully. I had set the alarms at 5 degrees above max running temp. Also worth noting the head temp varies up to 12 degrees at each end. Worth fitting dual sensors in my view.
I am a mechanic with nearly 50 years experience. I’m very impressed