Unless you blow air the correct direction you'll get no flow. If you want to test the inegrity of the cooler system do a flow test. There are other things that could contribute to poor flow if that is what you think is your problem.

Remove the rear cooler line at the trans and place in a clear plastic jug - like a clean empty washer solvent jug. Have someone start the engine and place in neutral. As soon as it starts flowing run it for 10 seconds then shut the engine off. A normal 1/2" system at 70F will pump no less than a quart in that 10 seconds. That tests the draindown valves, coolers and lines, valve body converter circuit and pump.