Either soldered copper pipe, or CPVC plastic (the cream colored stuff) will handle cooling system pressure and heat. Then use short pieces of hose on both ends to connect to the radiator, water pump, or whatever else there is in the system.
Jerry


"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!