Strange knob under hood
 

https://cimg1.ibsrv.net/gimg/minicoo...6d31038106.jpg
Hi everyone. Sorry as I’m a bit of an armature here. I’m trying to diagnose some overheating problems on my 2005 R53 but have never worked on a vehicle with something that looked like this. Any help would be greatly appreciated

Thats just the a/c pressure line. Thats to charge the a/c system. Most of the time if the ac is fine, you will never touch it.