i see that there is a switch in the bottom left side of the radiator on my stock 13b s4 i want to drop in my racing radiatior but it doesnt have ports for the coolant level sensor on top or that switch on the bottom. my haynes manual says that its a switch but doesnt tell its function. please help thanks oh and any help bypassing the coolant level sensor would be great too

 

I didn't hook that up when I switched to a KOYO as the rad didn't have a place for it either.
You are OK.
That sensor is for the ECU for temp,but is not Crucial.
The sender at the top of the stock rad is for LOW coolant and activates the buzzer in the cabin when low coolant is detected.Now,really you "should" have this sender.BUT if you have to get rid of it you can.To do this you take the single wire that goes off the Harness to that sender and attach it to Ground so the Buzzer doesn't activate.
Obviously you would not have any way of detecting low coolant now,so Watch your temps.