So my coolant filer neck has a nipple as it is an S4, that goes to the overflow tank. The nipple is now broken, by I got another one on the radiator.

So my question is: Can I block the nipple on the filler neck (on top
of the engine) and route the hose back to the radiator nipple, and be done with it. I searched and othe generations don't have that nipple on the filer neck, thus my question.

 

Did it, realised that is how it's done on an S5, never mind.

 

Make sure the radiator cap on the radiator is a pressure bypass type. Stock its just a sealed cap because the stock radiator doesn't have a nipple.

Also, Make sure you still fill the system from the coolant neck cap, it's higher up in the system.

 

Thanks for your input, that is exactly how I did it, considering it was not the same pressure for both caps, so I exchanged them. It should work fine.

At first I was worried that the nipple would not be at the highest point, but that how it is on the S5.