La Marzocco GS/3 steam died

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laservet
Posts: 103
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#1: Post by laservet »

I pulled 8 oz water from the tea wand, the pump started, ran, and quit like normal. However, I could hear water running continuously after the pump shut down. Steam pressure dropped to zero but the dial on the gauge read off the top end, dropped to zero when I opened the steam valve. Pulled the right panel and can see water running down a clear plastic tube, discharging steaming hot water into the right side of the drip tray. The water continues to run unassisted, at much less than line pressure (machine is plumbed in), machine on or off, until I cut the water off at the wall.

I'm not particularly mechanically adept but I have been inside the machine several times in the past, pump replacement, stuff like that. The manual isn't the most helpful without descriptions of parts. It seems to me it is acting like a fill sensor bit the dust, the boiler continues to fill, overfills and runs over, heater shuts off, and water gets in the little copper pipes to the gauge to screw up the reading. But again, it's not my field of expertise so I guess a stuck valve could mimic what I'm seeing.

Local repair guy will get a call tomorrow morning. He PM'd it a couple of months ago, cleaned all the probes, replaced leaky steam boiler popoff valve, found very little scale. In the meantime, I checked the connections to the sensors and they look OK as far as I can tell. Any ideas?

Ken Fox
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#2: Post by Ken Fox »

Here's a wild guess; your input solenoid has failed in the open position. Do you have an input pressure regulator on the mains input water? If your water pressure is too high and you don't have a regulator, this could kill an input solenoid producing symptoms conceivably like what you describe.

ken
What, me worry?

Alfred E. Neuman, 1955

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shadowfax
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#3: Post by shadowfax »

If water is flowing into the right side of the drip tray, there are only two candidates for the flow: the brew boiler OPV and the steam boiler safety valve (also an OPV, but set at 3 bars instead of ~12). The actual boiler safety valve on the GS3 is located right between the two boilers, just to the right of the 3-way solenoid on the back of the group's gooseneck. You'll see it immediately when you take off the cup warmer grate assembly. It's the metal cylinder with a little clear plastic hose coming out of the right of it routed to the drip tray.

Ken is most likely right: your auto-fill solenoid has failed. When this happens, the steam boiler fills up entirely and reaches line pressure, usually around 3-4 bars and much higher than the maximum acceptable steam pressure, which would be 2.5-3.0 bars. The safety valve opens and water gushes out. But you don't have any steam pressure, because it's just water pressure: water will just trickle out of the steam wand.

I'm still not seeing why your steam pressure gauge drops so low when you open the valve. I would guess this means that you have only a very slight leak in your autofill solenoid valve, and water is flowing into the boiler at a much lower rate than the steam wand discharges it, giving you 0 bars of pressure. I assume it builds back up when you close it back?

Also, this can be an intermittent problem if it is solenoid valve leakage: the valve might just have a particle stuck holding it open that may clear "naturally" as it opens and closes. You should probably have the valve taken apart and cleaned thoroughly or replaced, though, just to be safe.
Nicholas Lundgaard

laservet (original poster)
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#4: Post by laservet (original poster) »

Thanks. I assume since the pump doesn't come back on that rules out a bad fill sensor.

How do I cycle the solenoid? How easy is it to remove and clean?

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shadowfax
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#5: Post by shadowfax »

Yes, since the pump shuts off your fill sensor and fill logic is most likely intact.

The easiest way to cycle the fill solenoid is probably opening the left panel of the machine and disconnecting and reconnecting the wire from the fill sensor I believe it's a white wire, but basically you're looking for the wire that's clipped to a bare wire with a spade on the tip that's protruding from a fitting on the steam boiler. The pump will activate momentarily after you pull it and then close shortly after you reattach. You can do that as much as you want.

Cleaning and removal isn't fundamentally difficult, but with the tight space of the machine, it may well become somewhat challenging. You're looking to check out the solenoid labeled (I) in the first post of this thread. You'll want to take off the coil (the black part on top) and then unscrew the shaft from the base. To take the shaft off you'll need a large wrench, 22mm or something like that, and probably another tool to hold the base steady so you don't torque the pipes that are holding it in place. If you're not mechanically inclined, this might be best left to the professionals.
Nicholas Lundgaard

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erics
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#6: Post by erics »

Some cautionary comments from someone who does not own one of these machines:

First, I would drain some water from the steam boiler - about 1-1/2 quarts, assuming it is still full to the brim as you read this. I would count on replacing the steam boiler pressure gage - it has been severely wounded :(

The water level sensor probe for the GS3 is bent at a particular angle after it enters the steam boiler. You want to be a little careful not to rotate the connection because this would alter the normal water level in the boiler.

The fill solenoid for the steam boiler (from the pics I have seen) is a capped off brew solenoid valve and is intentionally installed "backwards". You might see a little arrow on the valve and it will likely be pointing in a direction opposite to that of normal flow. Unscrewing just the housing for the valve, as Nicholas described, is the safest & easiest procedure but a tech might opt to replace the entire valve. If so, be sure to note the orientation of the existing valve.
Skål,

Eric S.
http://users.rcn.com/erics/
E-mail: erics at rcn dot com

laservet (original poster)
Posts: 103
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#7: Post by laservet (original poster) »

shadowfax wrote:Yes, since the pump shuts off your fill sensor and fill logic is most likely intact.

The easiest way to cycle the fill solenoid is probably opening the left panel of the machine and disconnecting and reconnecting the wire from the fill sensor I believe it's a white wire, but basically you're looking for the wire that's clipped to a bare wire with a spade on the tip that's protruding from a fitting on the steam boiler. The pump will activate momentarily after you pull it and then close shortly after you reattach. You can do that as much as you want.

Cleaning and removal isn't fundamentally difficult, but with the tight space of the machine, it may well become somewhat challenging. You're looking to check out the solenoid labeled (I) in the first post of this thread. You'll want to take off the coil (the black part on top) and then unscrew the shaft from the base. To take the shaft off you'll need a large wrench, 22mm or something like that, and probably another tool to hold the base steady so you don't torque the pipes that are holding it in place. If you're not mechanically inclined, this might be best left to the professionals.
It looks in the picture like the coil has a brass valve coming out of the top. Do I remove this to remove the coil? I appreciate the advice, and those pics are extremely helpful as well.

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laservet (original poster)
Posts: 103
Joined: 18 years ago

#8: Post by laservet (original poster) »

erics wrote:Some cautionary comments from someone who does not own one of these machines:

First, I would drain some water from the steam boiler - about 1-1/2 quarts, assuming it is still full to the brim as you read this. I would count on replacing the steam boiler pressure gage - it has been severely wounded :(

The water level sensor probe for the GS3 is bent at a particular angle after it enters the steam boiler. You want to be a little careful not to rotate the connection because this would alter the normal water level in the boiler.

The fill solenoid for the steam boiler (from the pics I have seen) is a capped off brew solenoid valve and is intentionally installed "backwards". You might see a little arrow on the valve and it will likely be pointing in a direction opposite to that of normal flow. Unscrewing just the housing for the valve, as Nicholas described, is the safest & easiest procedure but a tech might opt to replace the entire valve. If so, be sure to note the orientation of the existing valve.
Thanks for the help. Is there an easier way to drain the steam boiler short of removing the drain plug at the base and opening the stopcock there?

Ken Fox
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#9: Post by Ken Fox replying to laservet »

How much easier could it be than that? You need to have a hose you can push to fit while the boiler is draining, and of course you would need to turn off and unplug the unit first, as well as turn off the input water source or the boiler will continue to fill.

ken
What, me worry?

Alfred E. Neuman, 1955

laservet (original poster)
Posts: 103
Joined: 18 years ago

#10: Post by laservet (original poster) »

Maybe not easier, how about lazier method? :)

I spoke with the tech at LM USA and he walked me through cleaning out the solenoid. Sadly, it appears the steam boiler gauge is toast since it was forced all the way around clockwise until it hit the zero post. New gauge is on the way, as is the new design drip tray cover. I'm off Thursday, will mess with it then and report back here.

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