[Kjell]

I wanted to check the integrity of my o-ring seals before I finished my 2L
engine build. So I assembled the engine just far enough to do so. The head was
on along with the front cover and H2O pump. I then temporarily installed
the TA and hooked up the radiator. I used a piece of hose to connect the heater ports together. I then borrowed a cooling system pressure tester to pressurize the system (after filling with H2O of course). After 1 hour at
11 PSI I saw no signs of leakage. Now to finish up assembly!

 

[ghnl]

Looking good!

My eL-cheapo version is to use a bicycle inner tube. Cut the inner tube opposite the valve stem and hook up the two cut ends to whatever you are testing. Add air via the valve stem & the inner tube inflates pressurizing whatever you are testing. Not as precise as your test but it does the job.

 

[Tifosi]

Just a quick note of possible import:

15 psi is the rad cap blow off point so you'd likely need to take it at least to there to be absolutely sure, otherwise both versions of testing show some darn good ingenuity.