Pressure no longer building during backflush

Did your new Mini work fine initially but have an in warranty (year one) problem later. Post here for advice. Later report on your fix. Posted photos documenting repairs are encouraged.
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lessthanjoey
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Pressure no longer building during backflush

Post by lessthanjoey » Sun Sep 14, 2008 4:33 pm

I've been pulling a lot of shots all week without problems (I have passive p/i - regular pressure ramp to 9 bar). Backflushes behave the same way.

This morning however, I decided it was time for the detergent backflush clean and on my first try the pressure gauge oscillated wildly around 1-2 bar and never got higher than that. Same thing when I kept playing. There's no water coming out of the portafilter and I don't notice any leaks. :-(

Suggestions?

My guesses are:
- Pump gone bad?
- OPV somehow opening far too early and in an unstable manner?

EDIT: The sound also never reaches the more "subdued" noise that's typical once the pressure is there.

Cheers,
Joe

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Re: Pressure no longer building during backflush

Post by admin » Thu Sep 18, 2008 7:49 am

Any breakthroughs on this issue?
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lessthanjoey
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Re: Pressure no longer building during backflush

Post by lessthanjoey » Thu Sep 18, 2008 11:01 am

I'd been away for a couple of days so hadn't had a chance to try anything the guys at Chris Coffee suggested.

Last night, however, I did get everything apart and adjusted the OPV a little in the hopes of kicking it free if something was stuck but no dice. Another call to Chris Coffee this morning.

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Re: Pressure no longer building during backflush

Post by lessthanjoey » Sun Sep 28, 2008 2:36 pm

I just got around to disassembling the expansion valve as recommended by Chris Coffee. Man, is that painful to get back in (threading the screw while pushing up against the spring. No dice. If anything it seems worse :(

I actually ended up tightening it all the way (it started twisting the entire assembling right at the end) in steps, checking pressure all along the way and it had nothing up until the last couple of tries which barely hit 3-4 bar.

I'll call Chris Coffee back on Monday morning, but I'm a little confused at this point - maybe the gauge is just really screwed up?

Cheers,
Joe

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chas
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Re: Pressure no longer building during backflush

Post by chas » Sun Sep 28, 2008 6:03 pm

I'm not sure about the CC suggestion to check the expansion valve. If it had failed somehow letting pressure leak there, you'd have water pouring out. I'm sure you would have noticed and mentioned that.

I have struggled several times to get that valve screwed back on myself. It is a pain to get the right leverage on it at that angle. What I finally discovered last time - assuming you have one - is to use a deep socket of the right size (just the socket, not the wrench). It gives you a lot more leverage and screwing it back in is a piece of "coffee" cake.
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Re: Pressure no longer building during backflush

Post by lessthanjoey » Mon Sep 29, 2008 1:34 pm

Chas,

Thanks for the suggestion on the socket - I'm sure that'll be a great help now!

I called them back this morning and they're going to send me a new expansion valve to try. Like you said, it seems unlikely, but I'll give it a shot. Beyond that it seems like it could really only be a misbehaving gauge or the pump, don't you think?

Cheers,
Joe

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chas
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Re: Pressure no longer building during backflush

Post by chas » Mon Sep 29, 2008 5:58 pm

You mentioned that in addition to the gauge reading low, no water was coming out. To me this pretty well lets the gauge off the hook.

It is surprising that CC is sticking with the expansion valve idea. There is so little to go wrong with that part. As you saw when you disassembled it, there is just a spring that pushes a rubber disk against the end of a tube. If the rubber isn't damaged and the circular impression of the tube in the surface of the rubber disk doesn't run off the edge of the disk, it should be good to go.

BTW: I was remembering my instructions wrong for easing the pain of reassembling this valve. From the S1 VII Website:

- Reassemble valve. This will take some upward pressure to get started. I pushed up on the ratchet handle with my left hand and turned the socket with my right hand in order to get the threads engaged.

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Re: Pressure no longer building during backflush

Post by lessthanjoey » Mon Sep 29, 2008 8:16 pm

By "no water coming out of the portafilter" I meant "around the backflush disk". Ie. it wasn't leaking out of the portafilter. It pumps plenty of water, and it vents with force when I turn it off.

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Re: Pressure no longer building during backflush

Post by chas » Mon Sep 29, 2008 8:44 pm

But now when you pull a shot the pressure in the gauge is still way low, correct?
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Re: Pressure no longer building during backflush

Post by lessthanjoey » Tue Sep 30, 2008 1:43 am

Yep. At most (with the expansion valve turned to almost full tight) I see 4 bars. I actually could see 6 after 45 seconds or so with a blank filter before I disassembled - not sure what to make of that.

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Re: Pressure no longer building during backflush

Post by lessthanjoey » Thu Dec 11, 2008 6:06 pm

Well, here we are many months later and the problem has finally been solved! :mrgreen: It's been a struggle but boy is it wonderful to have her back.

To be fair, a solid 4-6 weeks was my fault as I really didn't have the time to be struggling inside the machine so partway through debugging everything got put on hold.

In the end it was the pump. We went through everything else in the chain first because according to Chris Coffee I am the first person to have a pump failure on a Mini Vivaldi. Alls well that ends well!

Joe

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Re: Pressure no longer building during backflush

Post by Niko » Thu Dec 18, 2008 7:14 pm

Any pictures, Joe?
Love to see something like that on the Mini.
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