after many attempts to clean with Piezo liquid, my print head have many clogged nozzles. It is possible to clean with with an ultrasonic cleaner with distilled water and isopropyl alcohol in 30%
Many clogged nozzles indicates air in the lines.
Alcohol will kill your head. What you need to do is use SimpleGreen and then follow up with Flush and let the flush stay in for 48hrs. Clean the cleaning pad and wiper blade as well.