10-4. I’ll go hunt up a new radiator cap.
It’ll almost certainly be a Chinese one. They surely can’t screw up a radiator cap, right?
There is so much I want to say on this subject, but I am not going to...
As far as leak testing, go to your favorite FLAPS and rent/borrow a coolant system pressure tester. It lets you get the system to operating pressure without being hot so you can watch the gauge to see if there are leaks (pressure loss) and inspect the physical system for where the coolant is coming out.