[Richard]

Yeah, the location of the coolant fill makes it impossible to use a conventional pressure tester.

I have fought the same issue for years. There are a number of fittings and clamps on the turbo side od the engine that form a small drop of coolant when cold. Dry as a bone when running. Arrrrrggggggh.

I second the flour or white paper towel leak detection systems.

But if you want to pressurize, there is a ready path into the coolant system. Either be prepared with pipe fittings and endure some spillage OR drain the systems and use soapy water bubble detection technology. Look on the back of the radiator close to the lock. The blue hose is a direct path into the coolant system