Originally Posted by
DmaxMaverick
I've heard it said, "A man with one clock always knows the time. A man with two is never sure." (obviously from a time before synchronous digital clocks)
Are you sure the rear gage isn't calibrated correctly? How do you know either of them are calibrated?
Also, coolant will not leak like air, or perhaps not at all, and it may never actually see 15 PSI. If it remains a problem, it can be tackled later, with the engine installed and filled with coolant. I'd suggest doing the test then.