Screeching sound while pulling shots

#1: Post by **rogher** » November 21st, 2020, 10:29 am

Hello, I've just joined the forum to see if I can get any help.
I have a Rocket Cellini 2 (rotary pump, HX boiler, E61 head) which is plumbed-in after a filter. I decided to descale after a few years, although there was nothing to suggest that was necessary. Since then I've had an occasional screeching when pulling shots, a bit like the sound I get when doing a back-flush. This has recently become much worse and is almost constant now. When constant, it takes much longer to pull shots because hot water is being diverted into the drip tray. I assume the OPV is being activated due to a restriction somewhere. Does this sound familiar? What do I need to do to find and cure the problem? The grouphead seems fine (clean) but maybe I'm not looking properly.
My (UK) supplier does not want to know and lock-down makes this difficult anyway, so I feel that a DIY solution is my only option at the moment.

#2: Post by **bcrdukes** » November 21st, 2020, 12:25 pm

Sorry to hear of your troubles. I hope you can resolve this soon!

When the machine makes the sound, do you know how many PSI the gauge is showing? If you can post a video, that would help tremendously too.

#3: Post by **another_jim** » November 21st, 2020, 2:03 pm

The OPV (overpressure valve) screeches if it is is fouled and opens. This happens when the pump pressure gets high (e.g. when you backflush). However, in my experience, this happens to stand alone OPVs , I don't recall hearing about it happening to the ones built into rotary pumps. Open your machine up, and backflush. If your machine has a stand alone OPV; it's be screeching, and if it does, clean it. If the screeching is coming from the rotary pump, see if someone who's experienced fixing these can help

November 23rd, 2020, 4:10 pm

With a blanking disc inserted, the head group pressure rises from 9 bar to nearly 13 bar.

(hope the link works)

#5: Post by **another_jim** » November 23rd, 2020, 5:13 pm

Posting a video of a screeching sound is wasting everyone's time. Take the case off and search.

#6: Post by **bcrdukes** » November 23rd, 2020, 5:31 pm

OP - Try referring to thread as well. 13 bar is quite high.

Rocket Giotto (E61) "screaming" when brewing

You also mentioned that your machine is plumbed in - was it recently plumbed in, or has it always been plumbed in?

November 24th, 2020, 4:41 am

video of backflush

#8: Post by **pcdawson** » November 24th, 2020, 3:06 pm

another_jim wrote:Posting a video of a screeching sound is wasting everyone's time. Take the case off and search.

Let's face it, if we are reading posts on home barista we likely have time to waste

Listening to your second video, it sounds to me like the sound is mechanical and likely coming from the rotary pump. OPV issues sound more like a steam whistle on most of the machines I've owned. I would make it into a local repair shop. Good luck and please post on how this turns out.

#9: Post by **Randy G.** » November 24th, 2020, 3:56 pm

Because the sound starts immediately upon engaging the pump, I can't imagine that to be anything other than either motor bearings about to give up the ghost or a bad rotary pump.