You don't need to drain the antifreeze if you plan it right. You will loose a little antifreeze. Just have the new sensor ready to screw in and pull the old one, hold a finger over the hole and then quickly insert the new one.... Make sure the radiator overflow tank has plenty of antifreeze in it and keep a check on it for a week.
I have a 91 GMC pickup with a 350 engine and auto tranny. I had my
> mechanic do a checkup of the underside of the truck and he said the
> knock sensor is broken (the wire terminal corroded off). I asked him
> what it's for. He said it senses a knock in the engine and does
> something to compensate.
>
> He knows I am on a limited income and said I can change it myself if I
> want. He said I just need to drain the antifreeze because it screws
> into an antifreeze coolant port. Unscrew it, replace it, put wire on. >
> I agree this sounds pretty easy to do, but I cant understand how a
> thing inserted into a coolant path can sense a knock in the engine? >
> Can someone explain how this thing works.
>
> Thanks
>
> LM