3 BAR converts to 43.51131 psi = (lbs/sq.in)

You should not need to test at a higher pressure.

Air molecule density is lower than oil molecule's = it leaks easier in a water test tank given any escape path (crack)..

http://www.grc.nasa.gov/WWW/K-12/airplane/fluden.html

http://en.wikipedia.org/wiki/Density_of_air

http://academics.vmi.edu/chem_jt/CH131/density.htm

http://www.stevespanglerscience.com/experiment/seven-layer-density-column










Have a great day.

__________________
ASE Master Mechanic
asemastermechanic@juno.com

Prototype R&D/testing:
Thermal & Aerodynamic System Engineering (TASE) Senior vehicle instrumentation technician.
Noise Vibration and Harshness (NVH).
Dynamometer.
Heat exchanger durability.
HV-A/C Climate Control.
Vehicle build.
Fleet Durability
Technical Quality Auditor.
Automotive Technical Writer

1985 300SD
1983 300D
1984 190D
2003 Volvo V70
2002 Honda Civic

https://www.boldegoist.com/