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How to replace a heatbreak/heatsink/heaterblock (MK3S+/MK3S/MK2.5S/MMU2S)

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How to replace a heatbreak/heatsink/heaterblock (MK3S+/MK3S/MK2.5S/MMU2S)

How to replace a heatbreak/heatsink/heaterblock (MK3S+/MK3S/MK2.5S/MMU2S)
Relevant for:
Last updated 4 months ago
How to replace a heatbreak/heatsink/heaterblock (MK3S+/MK3S/MK2.5S/MMU2S)
 Difficulty
Moderate
 Steps
33
 Available languages
CSDEESFRITPL

Step 1 Introduction

Introduction
Introduction
This guide will take you through the replacement of the heatsink, heatbreak and heaterblock.
The guide is compatible with printers:
Original Prusa i3 MK3S+
Original Prusa i3 MK3S
Original Prusa i3 MK2.5S
Some parts might slightly differ. However, it does not affect the procedure.
All necessary parts are available in our eshop shop.prusa3d.com
NOTE: Read the instructions carefully. Some steps may vary depending on the type of replacement part.

Step 2 Tools necessary for this guide

Tools necessary for this guide
Tools necessary for this guide
Tools necessary for this guide
Tools necessary for this guide
To replace hotend parts, please prepare:
Needle-nose pliers for zip ties (1x)
Wrench size 16 EU / 0.63"  
Allen keys - 2.5/2.0/1.5 mm (1x)
Torque wrench (1x)
Standard Socket size 7mm EU / 1/4" US (1x)
Cloth or piece of fabric 15x15cm (2x)
The torque wrench has to be set to values around 2-3 Nm and is critical for the proper tightening of the nozzle. You can use a regular wrench, but there is a risk of damaging the hotend.

Step 3 Prepare the printer

Prepare the printer
Prepare the printer
Make sure that:
The filament is unloaded from the hotend (remove also the spool and the spool holder).
X-axis with the extruder is slightly above the middle of the height (Z-axis) of the printer.
CAUTION: In some steps, you will need to preheat the printer. Avoid touching the HOT parts!

Step 4 Partial disassembly of the extruder

Partial disassembly of the extruder
Partial disassembly of the extruder
Partial disassembly of the extruder
Partial disassembly of the extruder
In this guide, we won't disassemble the extruder completely. Thanks to the new design, it is enough to release the screws and move the plastic parts slightly apart.
Release and remove the M3x14 screw from the hotend fan.
Release and remove the M3x20 (M3x18) screw from the hotend fan. Note that the fan-shroud might fall off.
Leave the other two screws holding the hotend fan in place. No need to remove them.
Release and remove both screws and remove the Front print fan.
Carefully insert the Front print fan in the X-axis belt.

Step 5 Preheating the nozzle

Preheating the nozzle
Preheating the nozzle
Preheating the nozzle
Preheating the nozzle
WARNING: This and the next step are not intended for the HEATSINK replacement! Skip to Protecting the heatbed
On the printer's screen navigate to the Settings.
Open the Temperature menu.
Set the nozzle temperature to 275 °C by turning the knob.

Step 6 Releasing the nozzle

Releasing the nozzle
Releasing the nozzle
Releasing the nozzle
Releasing the nozzle
WARNING: Avoid touching the HOT nozzle!!!
Set the torque wrench to 3 Nm (26.5 in-lb).
Some torque wrenches are not intended for loosening. Read the instructions for your torque wrench. Alternatively, you can use a ratchet or a side wrench size 7 mm / 0.28".
With one hand, hold the heaterblock using the wrench size 16 (0.63"). Place the wrench under the cables to avoid damage.
With the other hand, use a torque wrench, place it on the nozzle and slightly loosen it. Do not remove the nozzle at the moment.
Navigate to the Preheat menu and at the end of the menu select Cooldown.
Wait for 15 - 20 minutes to ensure the hotend is cooled down completely before proceeding to the next step.

Step 7 Protecting the heatbed

Protecting the heatbed
Protecting the heatbed
Turn the printer off and unplug it!
Before these steps, it is recommended to protect the heatbed!
Take off the flexible steel sheet.
Use any cloth or piece of fabric, which is thick enough and cover the heatbed. This will ensure you won't damage (scratch) the surface during the disassembly.

Step 8 Partial disassembly of the extruder

Partial disassembly of the extruder
Partial disassembly of the extruder
Partial disassembly of the extruder
Partial disassembly of the extruder
In this guide, we won't disassemble the extruder completely. Thanks to the new design it is enough to release the screws and move the plastic parts slightly apart.
Release both screws, but don't remove them. We will use them to hold the extruder parts together.
Release both screws, but don't remove them. Just make sure they won't block the motor from moving.
Release the idler screw on the side to disengage it from the idler door.

Step 9 Partial disassembly of the extruder

Partial disassembly of the extruder
Partial disassembly of the extruder
Partial disassembly of the extruder
Partial disassembly of the extruder
Before you move any parts, make sure there is enough slack in the extruder motor cable!!!
If not, you have to cut the zip ties on the textile sleeve, open the box with electronics and make sure the motor cable is free to move.
Carefully move the extruder apart. First, pull the motor, then the lower part with the print fan.
Create a gap similar to the picture. Align the printed part holding the motor with the edge of the fan frame.
Reach for the hotend and incline its upper part towards the motor, it should slide out.
If the hotend is still stuck inside, release the screws more and extend the gap between the printed parts.
BE EXTRA CAUTIOUS with the hotend cables!!! You can break them! Use a small force to pull the hotend out. Don't bend the cables.

Step 12 Removing the PTFE tube

Removing the PTFE tube
Removing the PTFE tube
Removing the PTFE tube
Before you continue with this step, make sure the nozzle is loose.
Hold the heaterblock with one hand and start screwing the heatsink with the heatbreak out.
With the heatbreak out, press the black plastic collet down to release the PTFE tube.
Pull out the PTFE tube from the heatsink.

Step 13 Removing the heatbreak

Removing the heatbreak
Removing the heatbreak
Use the second cloth to protect the thread of the heatbreak.
Hold the heatsink and using pliers release and remove the heatbreak.
We are done with removing the old heatbreak, let's move to the next step and install a new one ;)

Step 14 Applying the thermal paste

Applying the thermal paste
Applying the thermal paste
Applying the thermal paste
Applying the thermal paste
Take the new heatbreak and apply most of the content of the thermal paste package on the long thread. Spread it evenly with a paper towel.
Do not apply the paste on the short thread!:
Incorrect application: the thermal paste is covering both threads of the heatbreak.
Correct application: the thermal paste is covering on the long thread of the heatbreak.
Applying the paste on the short thread can later lead to a gap between the heatbreak and the nozzle. The nozzle might then become clogged when the filament is loaded.

Step 15 Placing the heatbreak back in

Placing the heatbreak back in
Placing the heatbreak back in
Placing the heatbreak back in
Placing the heatbreak back in
Screw the long thread of the heatbreak (with the paste) into the heatsink. Ensure the entire thread is screwed in.
After you screw the heatbreak in, clean the excess paste on the surface of the heatsink.
To finish the replacement process jump to Reassembly of the hotend

Step 17 Removing the PTFE tube

Removing the PTFE tube
Removing the PTFE tube
Press the black plastic collet down to release the PTFE tube.
Pull out the PTFE tube from the heatsink.

Step 18 Removing the old heatsink

Removing the old heatsink
Removing the old heatsink
Removing the old heatsink
Removing the old heatsink
Hold the heaterblock with one hand and start screwing the heatsink out.
Avoid loosening the heatbreak from the heaterblock!
To hold the heaterblock firmly we recommend using the wrench size 16 (0.63"). Keep the wrench away from the cables to avoid damage.
We are done with removing the old heatsink, let's move to the next step and install a new one ;)

Step 19 Applying thermal paste

Applying thermal paste
Applying thermal paste
Before we install the new heatsink, clean the old thermal paste from the heatbreak.
Apply most of the content of the thermal paste package on the longer heatbreak thread. Spread it evenly with a paper towel.

Step 20 Reassembly of the hotend

Reassembly of the hotend
Reassembly of the hotend
Reassembly of the hotend
Screw the new heatsink on the heatbreak. Make sure the heatbreak is all the way in the heatsink.
After you screw the heatbreak in, clean the excess paste on the surface of the heatsink.
To finish the replacement process jump to Assembling the PTFE tube

Step 22 Disassembly of the hotend

Disassembly of the hotend
Disassembly of the hotend
WARNING: Do not pull the thermistor or heater cables. Follow the instructions!
Release the thermistor screw with the 1.5mm Allen key. Using the Allen key gently push the thermistor out.
Release the heater screw with the 2.0mm Allen key. Using the Allen key gently push the heater out.

Step 23 Disassembly of the hotend

Disassembly of the hotend
Disassembly of the hotend
Remove the nozzle from the heaterblock and keep it for later use.
Hold the heaterblock with one hand and start screwing the heatsink out.
We are done with removing the old heaterblock, let's move to the next step and install a new one ;)

Step 24 Reassembly of the hotend

Reassembly of the hotend
Reassembly of the hotend
Insert the thermistor to the new heaterblock and secure by tightening the lock screw.
Then insert the heater to the heaterblock and secure it by tightening the black screw. Make sure the heater hangs over on the right side, see the picture.
Ensure both thermistor and the heater are properly inserted and tightened!

Step 25 Reassembly of the hotend

Reassembly of the hotend
Reassembly of the hotend
Reassembly of the hotend
Screw the nozzle slightly in the heaterblock. Create a gap about 0,5 mm (0.02 inch), see the picture.
Secure the nozzle against movement with one hand.
With the other hand, screw the heatbreak with heatsink into the heaterblock from the opposite side until it touches the nozzle inside. Do not tighten anything by torque wrench at the moment.

Step 26 Assembling the PTFE tube

Assembling the PTFE tube
Assembling the PTFE tube
Assembling the PTFE tube
Assembling the PTFE tube
Now it is time to insert the PTFE tube back in. Note, that each end of the tube is different:
One end of the tube has "rounded" outer edge. This end must be inside the hotend.
Look at the other end, where the tube is drilled inside, the shape of the edge is "conical". This is the side, where filament enters the tube. This part must be outside the hotend.
Push the black collet in. Slide the tube all the way in and hold it!
Using the other hand pull the collet out and only then release the tube!!! THIS IS CRUCIAL for the hotend to work properly.

Step 27 Reassembly of the extruder

Reassembly of the extruder
Reassembly of the extruder
Reassembly of the extruder
Reassembly of the extruder
Place the hotend back inside the extruder. Ensure the orientation is the same as in the picture with cables on the left side.
IT IS CRUCIAL to ensure the hotend fits to the extruder-body!!! The printed part is shaped according to the hotend. See the second and the third picture!

Step 28 Tightening the nozzle

Tightening the nozzle
Tightening the nozzle
Tightening the nozzle
WARNING: This step is not intended for the HEATSINK replacement! Skip to the next step.
Plug the printer in, turn it on and preheat the nozzle to 250 °C.
WARNING: Avoid touching the HOT nozzle!!!
Set the torque wrench to 2.5Nm (22 in-lb).
With one hand, hold the heaterblock using the wrench size 16 (0.63"). Place the wrench under the cables to avoid damage.
With the other hand, use a torque wrench, place it on the nozzle and tighten it.
Navigate to the Preheat menu and at the end of the menu select Cooldown.
Wait for 15 - 20 minutes to ensure the hotend is cooled down completely before proceeding to the next step.

Step 29 Reassembly of the extruder

Reassembly of the extruder
Reassembly of the extruder
Reassembly of the extruder
Carefully and slowly push all the parts together. In case of any significant resistance, STOP immediately and check, which part is blocking the movement.
Check once again the correct position of the hotend. Look from below the extruder. The heater block should be oriented as shown in the picture.
Make sure the hotend thermistor cables (thinner pair) are going above the heater cables. If not, guide them according to the picture.

Step 30 Reassembly of the extruder

Reassembly of the extruder
Reassembly of the extruder
Reassembly of the extruder
Tighten both screws, but ensure no cable is pinched on both sides of the extruder.
Repeat the same approach on the front side. Tighten both screws. Ensure no cable is pinched.
Ensure all the parts of the extruder are tight and not moving. Pay special attention to the hotend!

Step 31 Reassembly of the extruder

Reassembly of the extruder
Reassembly of the extruder
Reassembly of the extruder
Reassembly of the extruder
Fix the fan in place using two M3x20 screws. Tighten both screws just slightly, we need to adjust other parts before fully tightening them.
Use the M3x14 screw to fix the fan in place. Don't overtighten it, you can break the fan's plastic casing.
Place fan-shroud back in the extruder. Fix it in place with the M3x20 (M3x18) screw.
Once all parts are seated, tighten both screws on the front Print fan, but be careful, you can break the plastic casing.
Tighten up the idler screw until it is approximately flush with the plastic part to set the idler tension.

Step 33 It is done!

It is done!
It is done!
It is done!
Great job!
Heat the printer up and try it out ;)

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