On May 2018, I replaced 0.4 mm nozzle with 0.8 mm Volcano nozzle. Two days ago my Prusa i3 MK2 started to develop non-stop printing failure. Slic3r setting could not solve the issue. Last night I noticed that the idler bearing was not turning which supposedly rotate with finger press.
After I disassembled the hotend, I inspected all components thoroughly. There was tiny leakage at the bottom of heat sink where the PTFE tube seats on. The black spot was leakage of ABS filament I have used for the last two days.
It pushes the PTFE tube up and removes clearance of the idler bearing of extruder. It causes reduction of pressure between extruder gear and the idler bearing, eventually drops the flow rate of filament and produces printing failure.
How to prevent it?