No milk flow on a Delonghi Coffee Machine caused by lack of steam


It is very frustrating when your Delonghi coffee machine just will not suck milk and just spits instead of producing a steady flow. Small domestic coffee machines use the Venturi Effect to suck milk and mix it with air to create froth. This requires a good steady flow of steam. So your first action is to ensure you have adequate steam volume. If there is adequate steam volume, then you can look at the coupling device or milk jug as being the problem.
But here we are concerned with poor milk flow caused by a lack of steam. There are various methods to assess the steam volume. I usually decouple the steam line and make a milk beverage. I can then gauge the steam volume. You probably know the usual steam output from you machine, so it will be obvious if there is not the usual steam output. 


The steam is produced in the horse shoe shaped flash boiler. The first thing you should do is ensure this is hot and heating. When the machine makes steam it pulses water into the flash boiler. The flash boiler is heated and reaches temperatures greater than 200 degrees. So water turns to steam vapour rapidly. You need to meter the flash boiler as it will feel hot even if it’s not functioning. This is because water goes through the thermoblock before it goes into the flash boiler.
If the flash boiler is heating yet no steam is exiting, The most likely issue will be scale build up on the outlet of the flash boiler. Zoom in on the photo below showing scale almost completely blocking the outlet side of a Delonghi flash boiler. This machine had very little steam output.

deLonghi coffee machine flash boiler scale blockage

This thermoblock had to be replaced and it resolved the issue. If the steam is exiting the flash boiler ok, then I would suspect the electrovalve on the steam output. This may be blocked or not opening. You can determine this by removing the steam tube before the steam valve and making a milk beverage. Occasionally I have found steam tubes blocked with scale as well. Lack of steam is simple fault to diagnose its just a matter of finding the failed or blocked component.

However, lack of steam or inconsistent steam can also be caused by a failing pump. In the Delonghi machines I have notes instances where the Ulka pump was not delivering a consistent flow of water to the flash boiler, this caused the steam output to fluctuate. Changing the pump may resolve the issue. Often this is the cause when a blockage is not the culprit. These Ulka pumps can appear to be functional but be suffering a reduced flow rate or fluctuating flow.

If you require your Delonghi Coffee Machine Serviced. Please call us at Outwest Coffee and we can repair it for you. We are in North Lakes, north of Brisbane and are open Saturdays.


Comments are closed.

    Your Cart
    Your cart is emptyReturn to Shop
    Independently verified
    1406 reviews