You need to see if the grounds are too spaced out.
If it is second hand you will have scale buildup. 10 Common Issues and How to Fix them Easily2 - Why Is the Espresso Coming Out Too Fast or Too Slow?5 - When I Turn On the Pump, It Makes a Loud Noise.6 - How Do I Adjust My Machine’s Steam Boiler Temperature?Figure out which direction increases the pressure, and which direction decreases the pressure. Only problem, the pressure is too damn high.First of all, the temperature of the water flowing through the group head is nicely around 92°C and the coffee is pressed with ~10kg (measured with a bathroom scales).Water flows too fast through the coffee, resulting in a very thin cream (<1mm). Some machines offer variable pressure but typically begin with water line pressure and pre-infusion will last about 5-7 seconds. If you feel comfortable strip the machine completely down and clean the boiler etc.I completely unmounted, cleaned and remounted it when I got it. There are alternatives, but they may not be the real deal. Coffee was even worse than what I got with coarse grind.Give it a really good clean out, especially around the group head. To play the part of a coffee snob, we could simply quote the SCAA and ask, “Where are the 9 BARs of pressure that are necessary to make authentic espresso?” In truth, we should take a bit closer look at current espresso makers by setting the margins – the lowest margin should be a low-cost entry-level model while the other one should be a high-end boutique espresso maker. If you use pre-ground coffee, you're completely removing the bloom from the process, and as a consequence, the coffee has too little hydrostatic resistance to limit the shot volume to reasonable levels.The reason a coarse grind ends up leading to better coffee in this circumstance is that you're at that point depending on a very fast percolation (in the chemistry-lab sense, not the coffeepot sense) for extraction, rather than the passage of pressurized water If, after getting a grinder and pulling shots with fresh coffee, you're still ending up with too-fast shots, you can find the overpressure valve inside the machine and adjust it.
If the BAR pressure is too high, the tastes will be weak and vice versa. If you feel comfortable strip the machine completely down and clean the boiler etc.By any chance are you leaving the portafilter with ground coffee in the group head while it warms up? Because of gravity, this air weight is pushing down on the Earth’s surface.
It would make a heck of a mess. A good barista can taste the espresso and know what changes need to be made for next time. One bar of pressure is equivalent to one unit of atmospheric pressure, which means the 8 bars is eight times the pressure at sea level.Many consider the sweet spot for making delicious tasting espresso shots as 15 bars of pump pressure. Too Little Pressure. If you are finding dirty water under or around your machine, Check the end of the drain hose to make sure it is not crammed up into the drain destination, or if you have the hose in a bucket, ensure that the end of the hose is not in the water. Long story short, all of a sudden the machine has stopped brewing properly and I am having a hard time troubleshooting the exact problem with the machine.
If the BAR pressure is too high, the tastes will be weak and vice versa. Be prepared for the unexpected.
Pump espresso machines are what you’re most likely to encounter at your local café, and they have added mechanics that use a pump to maintain the pressure of the water.Here is a great video comparison between pump espresso and steam espresso:Now that we know that a certain amount of pressure is needed to call our drink espresso, what other insights are there to learn about this pressurized process that is espresso brewing?To brew great cup of real espresso, a number of important things need to happen to allow human judgment to marry mechanical precision.The grind size will vary based on characteristics of the coffee such as age, bean variety, and the roast profile.
Controlling Pressure. If it needs cleaning, remove it and clean it.