I've heard conflicting information about how much vapor pressure exists inside a Cummins during normal operating temperatures. One guy said it was outrageously high while another said it can't exceed the radiator cap pressure rating. Is the pressure greater inside the engine than inside the radiator?

I've heard the same thing that sometimes the cummins water pump has been known to blow freeze plugs out...As for what causes it, why or how... I'm not sure...

Out of curiousity, how much pressure would it take to blow a preeze plug out? 100's? 1000's? of psi?

Not sure... Once again from all I can give is hear-say about this... I've got no experience of this yet... Like MnTom from over at www.dieseltrucksite.com had a freeze plug blow out of his truck while pulling his travel trailer up a grade. Here is a Opie Coolant Bypass mod for that reason... http://www.cumminsforum.com/forum/3rd-gen-performance-parts-discussion/95455-opie-bypass-kit-install-pics.html But how, what and why... I'm not sure...