Hoses seem ok . Don't think it's an expansion tank just the rad. I was out on it for about 20 mins before it happened. This is second time. First time thought the thermostat was problem cos when I took tank off it was out of its housing. May have dislodged it removing tank. Cable tie holding it in place now. New rad cap fitted. It lasted a lot longer this time, thought it was cured. Could it be as simple as pump not working and rad getting too hot and overpressured , finding a weak spot somewhere? Just can't see where is leaks from. Runs fine no leaks gets hot and seams to pour out.