jeff

The pressure test doesn't look at differences in pressure in different
parts of the system. Rather, you put a different cap on the radiator.
The radiator cap has a hose that is connected to an air pump (like a
baskball pump) and a pressure gage. Normally, the pressure does not go
down quickly. However, if there is a leak, the pressure will go down
quickly. So the pressure test tells if there is a leak, but has nothing
to do with differences in pressure in different parts of the cooling system.

You get the system pressure-checked, ask the tech what the pressure test
is, and what it tests and doesn't test.

Jeff