[damdfw]

I put my temp sensor in that hole and put a thermostatic fan control where you have your temp sensor. On the new CSX cars there is a pink wire with the alternator wires that will control the cooling fans. The original street cars have a bung on the bottom of the expansion tank for the fan control. If you had a heater I believe you would use your current temp sensor position for one of the heater hoses.

Basically, put some Teflon tape on that sucker and forget about it.