Just IMHO, but testing at 2.5 times the rated pressure seems like playing russian roulette with your heater core. The heater cores are known for being much more sensitive than the radiator when it comes to excessive pressures. I'd be hesitant to pressure test at 10psi, especially if I had any concerns with how accurate my pressure gauge/regulator is. More often than not I seem to recall hearing "whoops" stories about cores springing "sprinkler" like leaks. frown


~ Dan
1951 Chevy 3 window 3100
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"My Grandpa Carl's Truck and How it Became Mine"
1966 Chevelle (Wife's Hot Rod) | 2013 Chevy Silverado (Current daily driver)
US Army MSG Retired (1977-1998) | Com Fac Maint Lead Tech Retired (1998-2021)