The 0.4 mm brass nozzle in my Prusa i3 MK3 is worn out - the extrusion hole is visibly larger than the replacement nozzles I have to fit. So I’m trying to replace the nozzle.

Unfortunately the nozzle seems to be stuck in the heater block. So far I’ve tried:

  1. Heating the hotend up to 285 °C, rotating the heater block slightly and trying to unscrew the nozzle with a wrench. (I exactly followed the Prusa YouTube video on changing nozzles).
  2. Leaving the hotend at 285 °C for 15 minutes and trying again - I found some other reports online this had helped. However it made no difference in my case.

In an effort to try and remove the nozzle from the heaterblock, I’ve now accidentally bent the heatbreak, so I’m going to have to replace some or all of hotend. But I need to get the nozzle out, so I know which parts to order - if the nozzle breaks off in the heater block I’m definitely going to need a new heater block as well.

What else can I try to free a seized nozzle?

This is the original factory-fitted brass nozzle, and the hot-end was pre-assembled in the kit I received.

  • 1
    $\begingroup$ Make sure you're turning it the right way! If you're looking down at the extruder the nozzle unscrews CW, not CCW. $\endgroup$
    – user207421
    Commented Jan 7, 2020 at 3:51
  • $\begingroup$ Good point - however I am definitely rotating the right direction - CW. This is where following videos is a great help. $\endgroup$ Commented Jan 8, 2020 at 7:34
  • $\begingroup$ Nozzle clogged with ABS can be soaked in acetone. Regarding whole heatblock, all electronics would need to be removed first. But maybe this idea is still of some use... But to the point: if overheated PLA can change to black coal, then heating the setup up to 285 °C for long period seems to me like asking for trouble. Because all remainings sandwiched in the thread will change into obsidian, won't it? So I bet it depends on material, and maybe there is some chemical solution for that? $\endgroup$
    – octopus8
    Commented Feb 2, 2021 at 3:44

1 Answer 1


Try to,

First, remove the heat block from the extruder/heat sink. Heat the hot end to ~ 230 'C. Then try to unscrew the nozzle while holding the heat block with a wrench or plier. Be extra careful with the heat block and with the plier.


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