It is possible that you just pushed it out because your recovery tank was too full or doesn't have enough capacity---a tube 17 x 1.5 (od?) doesn't have much room----
Jerry may be right about the size of the recovery tank .
I had the same problem after a couple of WOT passes , the pressure at the upper rad hose with a double pass rad was enough
to push out about a quart of water . I put a 2 quart recovery tank in and the problem was solved .
Normal driving never never a problem , but that's no fun !