The T piece shown is plastic and is common to all trads of the era (My 4/4, +4 and Roadster).
Whilst in there, worth replacing with stainless steel. SiFab used to sell them ex-stock so I guess you will have to hunt around for one.
There is another plastic T piece on a Roadster cooling system that is unequal - the spur element is a lot smaller than the pipe it is connecting to. These have been known to break (Sorry, I cannot remember the TM user name of the gentleman who pointed this out to me). Well worth replacing this with stainless steel on any Roadsters so equipped. Again, you will have to hunt around for the part as SiFab was, AFAIK the only supplier.
