Nope It sucks fluid the easy way.. from the radiator hose that isn't restricted.. those leaks may well have been your problem as i surmised they would exist.. please let us know... thanksAfter pressurizing the system to 15 lbs overnight it had bled down to about 10 to 12 lbs this morning. I had three leaks showing. Two are so minute they didn’t drip onto the floor. One is the seepage through the lower water inlet where I fabricated it and the other was where the the lower water inlet bolts to the front side of the block around the rubber sleeve gasket. The main leak (and it made a puddle on the floor) was around he lower radiator hose clamp at the radiator neck. It was the easiest fix. The radiator cap tested fine. So I’m guessing depending on where the thermostat is when I shut it off it makes a difference whether it sucks fluid out of the overflow container or air through the places where it’s leaking?