i am installing one into a b18b1 block. on the c-speed site, they show a spot to tap on the alternator bracket. i can't work it in that area because the tight space (engine in the car). i went ahead and drilled and tapped a hole on the front of the block...one of the holes above the ac bracket. i didn't know if it was necessary to drill all the way through to coolant space. is it necessary to function properly, to have the knock sensor exposed to coolant? thanks. by the way, i know the hole i hit is not a oil channel in case i have to drill out some more.

 

Yes, the knock sensor is supposed to be in the coolant.

Hence the fact that you should empty the coolant when replacing one.