Have the hood off my Rocket replacing the pump and noticed that the valve on top of the boiler continues to hiss every so slightly after it has closed when boiler coming up to temp.

Is this normal?

Van G wrote:Is this normal?

The valve on the left (safety valve) should never hiss. The valve on the right (anti-vacuum valve) should hiss slightly as the machine is starting to build pressure, but should not hiss at all once up to pressure. You can try removing, disassembling, and cleaning. The pictured AV valve has an o-ring that might be replaceable if bad, but most people just replace the whole valve if it is malfunctioning after cleaning.

P.S.
Image above courtesy of Andreas (duenorth), posted in: Considering used ECM Giotto, but needs parts (Sweden)

Thanks. Have taken anti-vacuum valve off and disassembled. Have soaking in vinegar bath and will then give a light scrub.

Bath in vinegar and then some light scrubbing solved the problem. Thanks homeburrero.