Understanding the Symptoms
A coffee machine is a relatively complex piece of equipment. It combines heating elements or boilers, pumps, solenoid valves, group heads, gaskets, seals, and in many cases an integrated grinder. Each of these components can develop issues independently, but they also interact with one another in ways that can make diagnosis less straightforward than it initially appears.
The most useful thing you can do when your machine starts behaving differently is to describe the symptom precisely and consider when it started. Did the change happen suddenly or gradually? Has anything about your routine changed – different beans, grind settings, water source, or cleaning frequency? Some problems that appear to be faults are in fact the result of changed variables. Others are genuine mechanical or electrical issues.
The problems below are grouped by symptom type. Each includes the most common causes and a note on whether the issue is typically something a user can address or whether professional intervention is appropriate.
Problems with Extraction Quality
Weak or Watery Espresso
Espresso that lacks body, tastes thin, or is lighter in colour than usual is described as under-extracted. The most common non-mechanical causes are grind that is too coarse, insufficient coffee dose, or a distribution issue in the basket. Before assuming a machine fault, check these variables first.
If variables are unchanged and the problem has developed over time, the likely culprits are low pump pressure, a blocked or partially blocked group head, or scale buildup restricting water flow through the boiler or thermoblock. Pump pressure degradation is common in machines that have had heavy use over several years. It can be diagnosed with a pressure gauge and, if necessary, the pump can be replaced or recalibrated.
A machine that was pulling good shots and has suddenly started producing weak ones with no change to grind or dose is often showing signs of a pump issue or significant scale accumulation. Both warrant investigation.
Bitter or Burnt Taste
Over-extraction produces a harsh, bitter flavour. Before attributing this to a fault, check whether the grind is too fine, the dose too high, or the extraction time too long. These are the most common causes and are corrected by adjusting variables rather than repairing the machine.
If the taste has changed without any change to recipe, the brewing temperature may have increased. Over-temperature is usually caused by a faulty thermostat or temperature sensor. On machines with programmable temperature, check that the setting has not changed. On older machines, a failing thermostat can allow the boiler to overheat, which affects both extraction temperature and, in more serious cases, creates a risk of component damage. This is a repair job requiring a technician.
Persistent bitterness can also be caused by coffee oil residues in the group head from inadequate cleaning. If the taste is accompanied by a rancid or stale quality rather than simply bitterness, this is the more likely cause and can be addressed with a thorough backflush cycle.
Slow Extraction or No Flow
If extraction is noticeably slower than usual, or if water is not flowing at all, the group head or internal pipework may be partially or fully blocked. Scale buildup is a frequent cause, particularly in hard water areas. In mild cases, descaling may restore normal flow. In more severe cases, the scale may have hardened to the point where it requires physical removal.
A completely blocked machine that produces no flow at all may also have a pump failure, a faulty solenoid valve, or an electrical issue affecting the pump. If descaling does not restore flow, further diagnosis is needed before continued use.
Temperature Problems
Machine Not Reaching Temperature
If the machine takes significantly longer than usual to heat up, or if the ready light or indicator activates but the shot temperature feels low, the heating element or thermostat may be failing. In thermoblock machines, scale buildup can insulate the heating element sufficiently to impair heat transfer.
A heating element that is failing may draw current and appear to function while producing less heat than it should. This is one of the harder faults to diagnose without testing equipment. If you suspect a heating problem, do not attempt to open the boiler or interfere with electrical components yourself. Have the machine assessed by a technician.
Machine Overheating or Tripping
If the machine repeatedly trips the circuit breaker, shuts off unexpectedly, or feels unusually hot to the touch in areas that should not be warm, there is likely an electrical fault. A failing thermostat may not regulate temperature correctly, allowing the boiler to overheat. A short circuit can cause repeated tripping.
An overheating machine should not be used until it has been assessed. Continued use risks component damage, and in rare cases there is a risk of electrical fire. This is one of the clearest cases where professional repair is necessary.
Water and Leaking Issues
Leaking Around the Group Head
Leaking from around the portafilter during extraction almost always indicates a worn or damaged group head gasket. The gasket is a rubber seal that compresses when the portafilter is locked in, creating a watertight connection. Over time, the rubber hardens, flattens, or cracks and no longer provides an adequate seal.
Replacing a group head gasket is one of the most common and straightforward repairs on domestic espresso machines. It requires removing the shower screen and the old gasket, fitting a new one of the correct size, and reassembling. If you are comfortable with basic DIY tasks, it is possible to do this yourself using a gasket designed for your specific machine. If you are not confident, it is a quick and inexpensive job for a technician.
Leaking Inside the Machine
Leaks that appear as water pooling around or under the machine, or that are visible when the drip tray is removed, can originate from several sources: internal hose connections, solenoid valve seals, the boiler, or the pump. These require opening the machine to identify the source and should be handled professionally. Using a machine with an internal leak risks electrical damage and may cause more extensive problems.
Machine Not Drawing Water
If the pump runs but water does not flow into the group head, the problem may be an airlock in the system, a blocked intake, or a faulty valve. Airlocks sometimes occur when a machine is run with an empty tank and can often be cleared by priming the pump with fresh water. If the intake filter or tubing is blocked, cleaning may resolve it. A faulty intake valve or pump, however, requires replacement.
Steam and Milk Frothing Issues
Weak or Inconsistent Steam
Steam pressure that feels significantly weaker than it used to, or that fluctuates during use, can have several causes. The steam wand tip holes may be partially blocked with dried milk or scale – this is the most common and most easily addressed cause. Remove the tip, soak it in warm water or milk cleaner, and clear the holes with a thin pin if necessary.
If the tip is clear and steam is still weak, the steam valve may not be fully opening, or there may be significant scale on the boiler heating element affecting its ability to generate steam. Valve issues require replacement; scale in the boiler may respond to descaling.
Water Coming from the Steam Wand
Some water condensation in the steam wand is normal, particularly at the start of steaming. Purging a brief burst of steam before placing the wand in milk clears this condensation. However, if the wand produces significantly more water than steam, or if water continues to spit after several seconds, the boiler may not be reaching the correct steam temperature. This can be caused by a failing thermostat or, in some machines, a scale-insulated heating element.
Unusual Noises
Loud or Laboured Pump Noise
Espresso machine pumps produce a characteristic sound during extraction. When this sound becomes noticeably louder, more strained, or starts and stops erratically, it usually indicates that the pump is working harder than it should. This can be caused by partial blockages, scale buildup, or a pump that is beginning to wear out.
Pumps have a limited service life, measured in operating hours rather than years. In machines that are used heavily or that have not been maintained well, pump wear becomes apparent in sound before performance is significantly affected. Replacing a pump before it fails entirely avoids an abrupt breakdown.
Grinding or Rattling Sounds
Grinding sounds in machines without integrated grinders may indicate a foreign object in the drip tray or that a component has come loose internally. Rattling from the casing can result from a loose screw or panel. Neither is necessarily serious, but the source should be identified before the machine is used extensively.
In machines with built-in grinders, changes in grinding noise are worth noting. A louder grinding sound may indicate wear on the burrs, which affects grind consistency and should be addressed. Burrs are a serviceable item and can be replaced when they become dull.
Error Codes and Indicator Lights
Modern domestic and commercial machines often display error codes or warning lights that indicate specific fault conditions. If your machine displays an error code, consult the manufacturer's manual first. Many error codes relate to conditions that can be resolved by the user – empty water tank, full drip tray, or a prompt to descale.
If an error code persists after the indicated action has been taken, or if the machine displays a code not covered in the manual, this typically indicates a sensor, component, or software fault that requires professional diagnosis. Do not assume that continuing to use the machine once a persistent error code has appeared is safe, particularly if the error relates to temperature or pressure.
When to Repair and When to Replace
A question we are regularly asked is whether it is worth repairing an older machine or whether it makes more sense to replace it. There is no universal answer, but the following factors are worth considering.
For domestic machines, a repair that costs less than roughly half the replacement value of the machine is generally reasonable, assuming the machine is otherwise in sound condition. If a machine requires multiple repairs in a short period, or if the core components – boiler, pump, heating element – are all approaching the end of their service life, the overall repair cost may approach or exceed replacement.
For commercial machines, the calculation is different. A commercial espresso machine represents a significant capital investment and is central to daily operations. Repairing a commercial machine is almost always the more cost-effective choice compared to replacing it, particularly for well-made Italian or German machines that are designed to be serviced. The key is regular preventative maintenance rather than waiting for a complete breakdown.
If you are uncertain whether repair or replacement is the more sensible course, we are happy to give an honest assessment. We will not recommend a repair if we believe it does not represent value for money.
Getting a Fault Diagnosed
If your machine has developed a fault and you are unsure of the cause, the most useful step is to write down what you have observed: when the problem started, what the symptoms are, what the machine sounds like, and whether anything changed before the problem appeared. This information helps a technician diagnose the fault more efficiently.
At Wolentra, we work on both domestic and commercial machines. You can contact us to arrange an assessment. For common faults, we can often give an initial indication over the phone before a visit is arranged.