La Marzocco Linea Mini pump screeching when expansion valve is loose

Equipment doesn't work? Troubleshooting? If you're handy, members can help.
extrapresso

#1: Post by extrapresso »

Hey Everyone,

Just reinstalled the expansion valve on my Linea Mini after performing the Grafikus Coffeetec needle valve modification. During reinstallation, I noticed the pump will make screeching noises if the valve is too loose. I found that tightening the valve stops the screeching. Does anyone know why this might be? If I had to guess, I'd say the pump expects a certain amount of force pushing back on it for correct operation.

ira
Team HB

#2: Post by ira »

All I can think if is that if there is a restriction in the line feeding the pump, when you open the valve far enough the pump starts to cavitate. Maybe someone more familiar with that machine can come up with a better reason as while possible, that doesn't seem likely.