Filling the Cooling Circuit

Recently, we have moved to a new coolant solution from the one that may have been provided when you received the AON-M2. We advise you to switch coolants when performing the recommended coolant flush every six months. Perform a full coolant flush if switching types of coolant. Do not mix different types of coolant.

Required Tools & Equipment

  • A coin or large flathead driver
  • A small flathead screwdriver
  • 3 bottles of coolant (from Box A)

Do not use water alone or any other coolant mixture not authorized by AON3D. Do not mix or dilute the provided coolant, unless otherwise indicated on the coolant bottle or instructions sent from AON3D. Improper coolant can lead to potential failures, including: galvanic corrosion, algal growth, scale formation, and polymeric degradation. Any of these issues will negatively affect the performance of the cooling system and can lead to catastrophic component failure.

The cooling system takes 1.6L of coolant to fill. You may have additional coolant left after filling the cooling system. Keep this to top up the system over time.


Please note the safety warnings from the supplier and use any necessary personal protective equipment (PPE) while handling the coolant.

The coolant bottles come with a spout assembly to help pour the coolant cleanly. Part of this assembly is a small tube packaged with the coolant.

Koolance bottle and tube

To assemble the spout, first remove the cap. Inside there is a rubber nozzle. Remove this.

Rubber nozzle under cap

Carefully pop out the centre of the cap. Keep this centre piece if you want to reseal the bottle later!

Pop the centre of the cap

Take the rubber nozzle and place it on the bottle opening. Secure it in place with the cap.

Rubber nozzle in place

Take the clear tube and insert it into the nozzle. This is your completed setup for pouring the coolant.

Coolant ready to pour

Initial Gravity Fill

Disconnect the power cord shown in the figure below to turn off the pumps.

Pump motor power cord

Open the fill port of the pump reservoir with a large flathead driver or a coin. Pour coolant into the circuit until the reservoir is almost filled to the top.

Once filled, set the red speed controller dials, numbered from 1 to 5 and located on the rear face of the pump motors, to number 3.

Pour the coolant at a slow and steady pace to ensure that the coolant mixture does not spill.

Fill the pump

Pump Fill

Set the red speed controller dials, numbered from 1 to 5 and located on the rear face of the pump motors, to position 5 using a small flathead screwdriver.

Plug the pump motor power into the harness, and let the pump run until the reservoir level goes down.

The coolant pumps are not intended to be run dry. Avoid having the pumps run when the reservoir level is low.

Unplug the pump power to stop the pumps.

Add coolant to top up the pump reservoir.

Plug the pump in again to repeat the fill-pump cycle.

The pumps are most effective at driving air out of the system when the reservoir is near full before starting, so make sure to top up between each fill-pump cycle. If you find the pump is still unable to fill the circuit, cycling the pump power on and off a few times is effective at dislodging any air clogging the circuit.

After about three cycles, there should be enough coolant in the circuit to achieve “steady state” flow. At this point, you no longer need to cycle the pump on and off - simply keep refilling the reservoir as necessary as the air continues to flush out of the circuit. Decrease the pump motor speed dials to 3.

Continue filling the reservoir until no more large bubbles are visible.

Flush Out Any Remaining Bubbles

Bring the speed of the pumps down to 1. The flow should become laminar and bubble-free. Make sure the pump is as full as possible with coolant

Increase pump speed to 2 on one pump only. Watch for bubbles coming out of the printer (the left tube coming out of the printer) and out of the radiator (radiator-to-pump connection). Once there are no more bubbles moving through the system, increase the other pump speed to 2. Top up the pump reservoir with coolant if needed.

Repeat this process, increasing pump speed on one pump at a time, until both pumps have reached 4 (with both pumps at 5, you will not have a smooth flow and bubbles will become entrained in the flow out of the pump.).

With both pumps still at 4, leave the cooling system running for about 10-15 min to finish flushing any remaining bubbles.

Return the pumps to 1 for normal operation.

The pumps must be set to 1 during normal operation to avoid trapping air bubbles in the flow.

Pump speed set to 1 for normal operation

Check the Coolant Reservoir

Check the reservoir level on a regular basis. If the coolant level in the reservoir drops to half-full or below, refill the reservoir. If the coolant circuit lines have bubbles running through them, refill the reservoir at the back and flush the bubbles using the above procedure. The animation below shows what it may look like when the coolant circuit is lacking coolant.

A coolant circuit that needs to be topped up