Strange noise on Rocket Giotto R

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eliseujr

#1: Post by eliseujr »

Hi there!

I've recently acquired a Rocket Giotto R machine (rotary pump) and I wonder if anybody has any ideas on what could be causing this strange noise in the beginning of coffee extractions:
I tried contacting Rocket some times, but received no replies unfortunately.

Many thanks in advance for any feedback on potential causes.
Eliseu

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stefano65
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#2: Post by stefano65 »

I normally hear similar noises coming from the OPV when first pushed,
you might just have to move the screw a little to stabilize it
Stefano Cremonesi
Stefano's Espresso Care
Repairs & sales from Oregon.

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DaveC

#3: Post by DaveC »

It appears to coincide with an increase in pressure. There are 3 valves in the brew circuit before the group. 1 way valve, balanced bypass in the pump and the expansion valve. The 1 way won't make that noise. Expansions valves can, but that would not usually be accompanied by an increase in pressure, but more likely at peak pressure. For the expansion valve to be the cause, it would haver to be maladjusted at or below the rotary pumps balance bypass, rather than the 12 bar or so it should be. It can be confirmed by checking whether there is any flow from the expansion valve during the shot

Favourite for the increase in pressure like that and sometimes a sound, is the balanced bypasson the rotary pump, especially if it's sticking a bit and leaking. If you look at an exploded diagram, it's easy enough to remove and check/service.
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eliseujr (original poster)

#4: Post by eliseujr (original poster) »

Thank you for the suggestions Stefano and Dave!
I'll open up the machine side panels to check the OPV and also the pump balanced bypass!

JRising

#5: Post by JRising »

I've got to agree with DaveC. It sounds like your expansion valve is harmonic at some point during the "filling of the pre-infusion chamber" stage, thus the expansion valve/OPV is being opened at something less than the the max brew pressure you would want the pump's bypass valve set for. Make sure, as DaveC mentioned, the OPV is adjusted to something like 12 Bar, and that your pump is adjusted to something like 9.5 or whatever your extraction religion tells you.

eliseujr (original poster)

#6: Post by eliseujr (original poster) »

Hi guys,

today I opened the top and side panel of the machine to closely inspect the OPV and the pump.
Using a kind of stethoscope I determined that the noise was not coming from these two components, but rather the E61 group.
I opened it, cleaned all it's internal parts, applied food grade grease, reassembled everything and voilá, noise gone!
It seems the problem was due to lack of lub on one of the grop valves. I suspect the one on the pre-infusion chamber.
I was using cafiza to backflush once a month, but looks like I have to reduce its use even further.
Many thanks for the suggestions!

Cheers!