what I would do
I haven't tried this, so please try it at your own risk.
What I would do is get a temp sensor and a gauge first, apply thermal paste on the radiator in an area nearby the stock sensor (was it top left?), stick your new sensor on it, and isolate it by any means such that the reading will not be too much affected by the environment (go creative with play-
Then I would disconnect the fan and run the engine till the temp light is on. At this point the temp inside the radiator is supposed to be 110 degrees celcius (please refer to the manual for the exact temp stated by the manufacturer). Measure the reading of your gauge, substract it from the supposedly actual temp and see the deviation between the two figures. Record it somewhere to use for further readings. Switch off the engine, connect the fan and re-run the engine to cool it.
I would NEVER upset the integrity of the radiator (drilling holes, sticking in cables, etc. for two basic reasons:
a) any stuff intrduced in the system has the risk of polluting it (due to corrosion),
b) you would have a hard time preventing leakages after any intrusive modification.
Let us know the results if you decide to do it.
Last edited by Goblin; 13 May 2008 at 12:57.