[glennpm]

Originally Posted by Oldtmtech

Being an old tractor guy I can tell you all steam boilers are hydro tested meaning the boiler is filled with water then air pressure the reason being is because water does not compress so if you have a leak the pressure quickly drops because your air vessel is small
If you just filled it with air pressure and you have a leak it is like when you lose a hose off of your air compressor tank and the hose whips around for ever
Your air compressor tank is a certified pressure vessel your engine block is not
Kind of a crude explanation but I hope this helps
Todd

Exactly correct Todd.