My 6 year old Delonghi ESAM330 failed me this morning. When the coffee machine breaks it’s a household emergency requiring immediate attention.
The symptom: when it turned on, the pump was working but water would not come out of the coffee dispenser nozzles, nor out of the water/steam nozzle. But water did flow into the drip pan.
The root cause: the high pressure side of the pump has 2 pipes. One goes to the system, the other is a high pressure safety bypass that works similar to the oil pressure relief valve in many cars. It has a spring pushing on a valve seat. If the system pressure gets too high (for example a pipe is clogged), the pressure works against the spring to open the valve and allow water to drain into the drip tray.
A picture’s worth 1,000 words:
You can see the spring inside the pressure relief line pushing to the right, on a little piston having a rubber seat on its face that blocks the high pressure port. That piston got stuck and wasn’t pushing against the valve, so the pressure relief valve was always open.
I removed the entire pump from the ESAM3300, then removed the large vertical white tube assembly that passes through the metal section, then removed the 2 valves at the top (the top double-U section unscrews from the rest of the white plastic). I removed the o-rings, disassembled the part including the spring and piston and soaked all the parts in 30% vinegar. Then rinsed them off, blasted out the lines with water and air pressure, applied Trident silicone grease (food grade, the same stuff I used to service SCUBA regulators) to the o-rings and seals, and reassembled everything.
When I turned it on and did a function test, the pump made a horrible metallic clacking sound. Oops! Looks like the pump must be primed. I filled a syringe with water and inserted it into the water input hose to the pump. I applied pressure to the syringe plunger until the line was pressurized, then turned on the ESAM3300. As the pump actuated, the line pressure I was applying with the syringe primed it.
It’s working like new again. Coffee emergency resolved!