Need Part Look Up Help
 

I am installing a Carrera oil cooler into my SC without the fan and need to plug up the hole that the temp probe goes into. One person thought it might be a 14mm drain plug that I need, but can anyone confirm the correct size before I run to the store? This is for the hole at the top of the oil cooler, facing the front of the car when installed. Normally the temp probe that works in conjunction with the fan goes into this hole.

Thanks.