Radiator pressure test stats

New to this forum but had my 2006 Tundra since new. Great truck but after 14 years it's beginning to have a few break downs. Not complaining, got my nickels worth from it for sure. Right now, i'm having a coolant disappearance issue. Went and bought a new cap today and did a pressure test on the radiator but couldn't find any info on what pressure it should hold at. I pumped it up to 10lbs and it dropped back to 5lbs but held. I bought a new cap several years ago when it was losing fluid then and still had to add coolant every now and then. No coolant in the oil,( i change my own oil) no coolant leaks that i can find. Replace radiator some years back when a leak happened with a cracked in the top of the radiator. Could not see anything obvious for leaks nor did i smell anything. So does anyone know what the hold pressure is for this truck's radiator?