Hi all this part of off S Type's my coolant system as it dumped the lost at the weekend.
It connects the coolant expansion bottle pipe to a kind of coolant manifold. Please see images attached.

Many thanks everyone.

 

I've moved your question from General Tech Help to S-Type forum. Members here with the same model will be able to help.

Graham

 

It's generally called the tank turret and is a very common failure spot.

See this thread (and others if you search) for info https://www.jaguarforums.com/forum/s...ghlight=turret

 

Mine broke off on my XJ6 3.0L just cleaned it up used a load of epoxy and a tie wrap to help it cure. still there although engine hasnt run in over a month.
New one was near £100

 

Replace the entire Upper Radiator Hose Assembly. The plastic gets brittle with age and heat cycles. If you try to fix it, it will come back to haunt you by failing somewhere else on the assembly. I ordered one for $68 off eBay not quite a month ago, part no. XR854920. The seller was Impart Inc. in the Atlanta area, phone (770) 948-8353.

These assemblies supposedly fit the 2003 through 2008 S-Type 3.0 cars, but be sure to verify that before you place your order....

Good luck....