How to Take Apart a Flooded Nozzle (Standard UM2 Nozzle)

(These instructions do not apply the the  Ultimaker 2+ or Extended +)

If your UM2, UM2 Extended, or UM2Go nozzle has flooded, you will not be able to take it apart cold. 'Flood' is the term we use when filament has leaked into inappropriate parts of the nozzle assembly. The white coupler and the nozzle block meet inside the silver isolator nut. When situated properly, filament moves through a contained path. During a flood, filament seeps out of that path through a small gap. The coupler rises and a plug of filament forms. When this occurs, liquid plastic oozes into the threads between these two components. When the nozzle cools, the plastic hardens, essentially adhering the two pieces together. 

The plug of filament will keep your printer from extruding consistently. To fix a flood, the nozzle, isolator, and usually coupler will need to be replaced. Due to the hardened plastic in the threads, it is impossible to disassemble the hot end while it is cold. These disassembly instructions are for flooded nozzles only. Please do not perform maintenance on a hot nozzle unless absolutely necessary. Regular replacement instructions can be found here. If you are uncertain about the names of the different parts in the hot end, you can find diagrams here. 

You can do quite a bit of the disassembly while the machine is still cold. Follow these steps BEFORE heating the machine.

1. Remove the four screws that hold the fan shroud. 
2. Remove the four thumb screws that go down through the black print block.
3. Unscrew the two screws securing the top part of the metal holder. This will free the spring.
4. Make sure the nozzle and bottom part of the holder are not touching any wires and that no wires are in contact with the rear fan.  

Follow these steps to heat the nozzle and work hot. Remember, do not directly touch any of the hot components. 

1. DO NOT TOUCH THE NOZZLE OR HOLDER AFTER YOU HAVE RAISED THE TEMPERATURE. Using the menu MAINTENANCE-> ADVANCED-> HEAT NOZZLE, set the nozzle temperature to at least 230 degrees. If you experience difficulty with the remainder of the disassembly, raise the temperature to 260 degrees.
2. Using pliers, grasp either the nozzle block or the metal holder.
3. For this step you need a small screwdriver or one of the allen keys from your accessory bag. Unscrew the isolator nut by using the tip of the screwdriver in the holes of the isolator.
4. If filament has come in contact with the set screw in the nozzle block, use the 1.5mm allen key (smallest) to remove the set screw at this time.

Follow these step AFTER the machine has cooled.

1. Use the menu to set the nozzle temperature back to 0. Be mindful that the hot nozzle does not come in contact with any wires. When the machine indicates that the nozzle temperature is at or below 20 degrees (which is room temperature) you may continue. 
2. Remove the heater cartridge and temp sensor from the nozzle. If the temp sensor (smaller wire) breaks, click here for directions on how to replace it.
3. Insert the heater cartridge and temp sensor into the new nozzle. The sensor is fully inserted when you can no longer see the metal tip. The heater cartridge is fully inserted when the white gap of cord in the metal connector is against the nozzle block. Hold the heater cartridge in place while tightening the nozzle set screw. When finished, make sure the wires are still fully seated.
4. Push the coupler into the isolator until they're flush. Place the isolator through the holder and screw it onto the nozzle block. Stop when only one thread is visible.
5. Ensure the isolator is flat against the holder bottom. Put one end of the spring on the coupler and seat the other inside the recess in the holder top. Screw down the holder top with the 3mm screws (two larger ones).
6. Hold the print block together. The linear bearings that run through it should be centered in the block. They are shorter than the print block, so don't line them up with the edge. Put the metal  holder in place. Watch the fan cords; it is easy to pinch them between the print block and the holder. Reinsert and tighten the thumb screws.
7. If you do not have a white PTFE ring, follow the directions in step 8. If you do have a white PTFE ring, put this in place in the fan shroud. Screw the fan shroud in place using the 4mm screws (smallest ones) and move to step 9.
8. If you do not have a PTFE ring, you'll have to make sure the nozzle is not touching the fan shroud. Start each of the 4mm screws (smallest) that hold the fan shroud on. Look underneath at where the nozzle goes through the hole in the fan shroud. Center the nozzle so the two are not in contact. Then tighten the four screws. Once they are tight, check and make sure the nozzle hasn't moved.
9. Make sure none of the cords are pinched between the holder and the print block, and ensure that none of the wires are in contact with the rear fan. 
10. Reseat the Bowden tube, making sure that it goes all the way down to the PTFE coupler and doesn't get caught on the metal plate above. Then replace the blue clip.