Do you have a parts basket in your ultrasonic cleaner. The part cannot just be setting on the bottom of the tank it needs to be suspended. Also ultrasonic is not for removing heavy crud. Use a wire brush and solvent for that. Ultrasonic cleaning is great for getting into the tiny small places and getting that last bit of grime off open areas.
Lastly are you sure that ultrasonic machine is functioning? If it is you should see a very slight shimmer in the water. I use a bit of dawn dish soap with warm water in mine and it really cleans. But it is not quick. The parts are in the solution for an hour or two.
