The lack of coffee flow from the dispenser spout when the pump is running and there is water in the tank is a direct signal that the hydraulic system is clogged or the pressure in the brewing circuit is critically low. Most often, the problem lies in hardened coffee oils that have blocked the passage holes in the brewing unit, or in airing pumps, which physically cannot push water through a compressed tablet. In automatic models DeLonghi, Saeco or Bosch it may also indicate a flow sensor calibration failure that erroneously stops the flow process, thinking there is no water.
Ignoring this symptom will result in overheating of the heating element (thermoblock) or boiler, since water stops circulating and cooling the system. Prolonged operation “dry” with the valves closed is fraught with rupture of the seals or failure of the solenoid valve. Therefore, if the coffee machine hums, but no coffee comes out, you must immediately stop trying to start the preparation program and proceed to diagnosing the hydraulic circuit.
Primary diagnosis and external factors
Before disassembling the device, you should exclude trivial but common reasons for stopping the liquid supply. First of all, the water level in the tank and the position of the float are checked, which can stick in the lower position, sending a false signal to the control board that there is no liquid. It is also worth inspecting the tank itself for cracks in the water intake area, through which the pump can suck in air instead of water, creating the so-called air lock.
The second important aspect is the quality and degree of grinding of the beans. If in the settings coffee grinders The minimum grinding (finest) is set, coffee particles turn into dust and, when pressed, form a monolithic crust through which water under standard pressure simply cannot pass. In such cases, the machine may attempt brewing and make the characteristic sounds of a pump, but at the end you will only get a few drops or a dry tablet.
- 🔍 Check the position of the float in the water tank and make sure it moves freely.
- 🌡️ Make sure the car is warmed up and the readiness indicator lights up evenly.
- ⚙️ Temporarily increase the grinding degree of the coffee grinder by 1-2 divisions towards larger grains.
- 💧 Use bottled water of medium hardness to prevent scale formation in narrow channels.
⚠️ Attention: If you hear a loud whistle or squeak when you turn on the brewing program, this indicates that the pump is working at maximum power, trying to push water through a coffee tablet that is too dense. Stop the process immediately to avoid burning the pump motor.
Brewing unit: cleaning and maintenance
The main unit responsible for generating pressure and pouring water through the coffee is the brewing unit (BCU). During operation, the walls of this unit are covered with a layer of coffee oils and fine fractions, which over time harden and turn into a cement-like mass. If the coffee machine does not pour coffee, in 80% of cases it is necessary to remove the brewing unit and thoroughly rinse it under warm running water without using detergents.
Particular attention should be paid to the mesh filter and sealing rings. Microholes often form on the mesh, which are visually invisible, but critically affect fluid permeability. Gent brushing with an old toothbrush will remove plaque. If the machine has been used for a long time, the rubber seals may have lost their elasticity and swelled, which also prevents normal water flow and sealing of the system.
☑️ Checklist for cleaning the brewing unit
After cleaning, it is recommended to run several cycles of hot water without coffee (Hot Water or Rinse function) to flush out any remaining dirt from the internal channels. If after this procedure the pressure is restored, then the problem lies precisely in the hydraulic resistance of the contaminated unit. The frequency of this procedure depends on the intensity of use, but on average it is once every 2-3 months.
Problem with the pump and air in the system
Centrifugal or vibration pumps installed in coffee machines are extremely sensitive to the presence of air in the system. If the water tank is completely empty during operation or the machine has not been used for a long time, an air pocket may have formed in the hoses. In this case, the pump runs idle, creating noise, but does not pump water to the boiler. To eliminate it, you need to carry out a procedure deaeration (bleeding) systems.
The pumping process usually involves forcibly drawing water through the intake tube. Some models Philips or Saeco this is done through the service menu or a combination of buttons; in others, you need to remove the water intake tube, lower it into a container of water and start the flow until there is a smooth stream without “spitting”. It is important to ensure that no debris from the bottom of the container gets into the hose.
| Symptom | Probable Cause | Solution method |
|---|---|---|
| The pump is humming, there is no water | Air lock in the circuit | Bleeding the system through the intake tube |
| Weak jet pressure | Cappuccino maker needle or spout is clogged | Mechanical cleaning with fine wire |
| Coffee flows in drops | Grind too fine or grain too old | Adjusting coffee grinder burrs |
| Noise and vibration | Pump wear or scale in valves | Decalcification or node replacement |
How to bleed a pump without the service menu
Remove the water intake tube from the tank. Place it in a glass of warm water. Turn on the “Steam” or “Hot water” mode. The pump will begin pumping water from the glass. Hold until a smooth stream without air bubbles appears.
Scale and the need for decalcification
Scale is the main enemy of any coffee machine, especially in regions with hard water. Calcium and magnesium salts are deposited in the heating element (thermoblock) and in narrow water supply channels, gradually narrowing their lumen. When the channel diameter becomes critically small, the flow resistance increases so much that even a powerful pump cannot provide the required pressure, and the coffee stops flowing or flows extremely slowly.
Modern machines are equipped with water hardness sensors and a counter of prepared cups, which signal the need for a decalcification procedure. Ignoring the indicator CALC CLEAN or similar causes the machine to block the coffee brewing function to prevent emergency rupture of the tubes from overpressure. The use of special liquids for descaling allows you to dissolve deposits and restore the permeability of the system.
It is important to use only certified products, since aggressive household chemicals (citric acid in high concentrations, vinegar) can damage rubber seals and aluminum parts of the boiler. After the decalcification cycle, it is imperative to run 2-3 tanks of clean water in order to completely flush out the remaining dissolved scale and chemicals from the system.
⚠️ Attention: Never try to break through a blockage in the pipes mechanically (by blowing with compressed air under high pressure) without disassembling the machine. This can cause the plastic fittings inside the case to break off and flood the electronics.
Solenoid valve malfunctions
Electromagnetic valves (solenoids) are responsible for the distribution of water flows in the coffee machine. Their task is to direct water either to the brewing unit, or to the cappuccino maker, or to be discharged into the pan. If the valve responsible for supplying water to the coffee is “stuck” in the closed position or its winding is burned out, water will not physically flow to the caffeine. This often happens after long periods of downtime or power surges in the network.
Valve diagnostics require a multimeter to check the integrity of the winding and the presence of control voltage from the board. At home, you can try to “stir” a jammed valve by turning the steam and hot water supply modes on and off several times, creating pressure differences. However, if the valve has failed electrically, only replacing it will help.
When replacing valves, pay attention to the coil voltage (usually 12V or 24V) and connector type. Externally identical valves may have different flow characteristics.
Failures in electronics and flow sensors
In automatic coffee machines, complex electronics are responsible for the preparation process, which is based on sensor readings. A flowmeter measures the amount of water passing through the system. If it is contaminated with coffee dust or malfunctions, it may transmit incorrect data to the processor, for example that water has already been supplied, although in fact its movement is blocked. As a result, the control board stops supplying voltage to the pump.
Software failures are also possible, especially after power surges. In such cases, a full reset to factory settings helps (Reset) or flashing the device at a service center. If specific error codes appear on the display (for example, flashing lights in a certain sequence), you must refer to the instructions for your specific model Breville, Nivona or Miele for decryption.
If the machine makes operating sounds, but there is no coffee, the problem is mechanical (pump, clogged). If the machine is silent and does not start the process, the problem is in the electronics or sensors.
Frequently asked questions (FAQ)
Why does the coffee machine hum but no coffee comes out?
A humming sound indicates the pump is working. If the coffee does not come out, it means that water is not entering the brewing unit. Reasons: an air lock in the system, coffee grinding too fine, which clogged the filter, or a breakdown of the pump itself, which hums but does not pump.
Can citric acid be used for cleaning?
The use of pure citric acid is not recommended, as it can crystallize in the components and damage the rubber seals. It is better to use special coffee machine decalcifiers that contain corrosion inhibitors and are food safe.
How often should the brewing unit be cleaned?
It is recommended to remove and wash the brewing unit with warm water every 1-2 weeks during active use. Deep cleaning with soaking in tablets to remove oils is carried out once every 2-3 months or at a signal from the machine.
What to do if the pressure has not been restored after cleaning?
If mechanical cleaning and descaling do not help, the problem is likely a worn pump, faulty solenoid valve or flow sensor. In this case, diagnostics are required at a service center using a pressure gauge.