2001 Deville Crossover mishap
 

While attempting to block the upper radiator hose housing, on the crossover, I placed a mouse ball in the opening and it proceeded to roll away out of sight. I took off the thermostat and water pump , but, no sign of the ball. The ball is 1/2" diameter steel covered in rubber. It does not float. Does anyone know where it could have ended up???

I don't understand what you were doing, If your lucky you might find it if you remove crossover, most likely in cylinder head.

Thank-you Slowroll. I was attempting to pressure and smoke test the block only. I had already discovered that the radiator leaked intermittently and the neck of the coolant reservoir relieved pressure before the 18# cap. After web surfing I became convinced that the head gasket was bad although no white smoke and the car runs great all winter. I believe that the ball made it to the head as you suggest. If I leave it there will it possibly end up at the thermostat? I appreciate your reply. Thank-you

Slowroll, You had correct location for the location of the steel ball. I snaked it out with a super magnet wired through 1/4" rubber house extended to the head. I snagged the ball on the first attempt. Thanks again