My silvia is at least 8 years old and is serviced on a regular basis
I am very careful with the amount of coffee, the grind, and tamping in the basket and sometimes it comes gushing out. Other times it extract beautifully. What is wrong?
Coffee Makers & Espresso... - Rancilio - Silvia Espresso Machine
Answers & Comments
The 'group seal' in the underside of the head that the grounds arm compresses against probably needs replacing. If you unknowingly left a few grounds to dry on the underside of the seal the last time you used the machine, this can be enough to cause a leak the next time around.
If replacing the group seal, replace the 'shower screen' above it as well. Always buy genuine Rancilio parts, you should be able to find both for around $10 - $15 each on Ebay.
There are videos on either You-Tube or Gooble that show how to replace these parts on the Silvia.
Always try to ensure the seal face is cleaned before and after use and the group seal will last longer, but they are actually meant to be replaced whenever necessary, they are not designed to last forever.