La Marzocco GS3 constantly heating

Equipment doesn't work? Troubleshooting? If you're handy, members can help.
maccompatible

#1: Post by maccompatible »

My GS3 was bought new in March of this year, and I'm still trying to learn about routine maintenance. It started leaking a couple weeks ago so I called LM and they helped me diagnose the problem as the vacuum breaker. I turned it off and planned on taking it to be repaired by a certified LM tech. However, I read up on how to service it, and it sounded easy enough. So I gave it a shot. I took off the vacuum breaker, disassembled, and noticed how dirty the inner pieces were. I scrubbed them quite a bit and put the whole thing together. It seemed like MAYBE I didn't tighten the fittings as much as they did at the factory, but I didn't see any leaks around the fittings as it returned up to temperature/pressure.

So the cleaning seemed to do the trick. I'm losing no more water out of the vacuum breaker, and it isn't constantly refilling the brew boiler. I also don't see any leaks or drips inside or under the machine. HOWEVER, now it seems like it won't turn the heating element off and the pressure is fluctuating between 9 and 12 bars pretty rapidly. If I turn it off, the pressure falls to 6 bars pretty quickly, and then more over the next couple of minutes while the steam boiler stays perfectly at pressure..

What could be going on? Did I maybe not fasten the fittings hard enough and I just need to get back in there and crank it? Is there another piece (gasket??) that's failed and it still needs further servicing? Any help would be much appreciated!
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Mayhem

#2: Post by Mayhem »

The vacuum breaker is fitted to the steam boiler and shouldn't be able affect other parts of the machine. If you're having issues with the brew boiler, there must be something entirely different going on as well.
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maccompatible

#3: Post by maccompatible » replying to Mayhem »

I kinda suspected that. Thanks for the input. I'm still not overly familiar with how it all fits together, so I wasn't aware it was actually connected to the steam boiler. So what else could be going on? Any ideas?
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AssafL

#4: Post by AssafL »

9-12 bar is the hydraulic (brew) circuit and boiler.

The vacuum breaker is part of the pneumatic (steam circuit).

Also - if the pressure oscillates 9-12 bar it seems that the heating element does turn off. Otherwise it will go up to 12 and stay there. As the water heats up the pressure will try to get higher but the expansion valve will release it as drops.

What does the temp reading show?
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sluflyer06

#5: Post by sluflyer06 »

idle pressure between 9-12 is normal, doesn't sound like an issue to me.

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Peppersass
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#6: Post by Peppersass » replying to sluflyer06 »

Maybe. I see more like 6-9 BAR a idle, but my machine is a lot older than yours and isn't an MP.

You should make sure the expansion valve is properly adjusted. The expansion valve is just above the far right-hand side of the drain box. You can see its round brass lower fitting peeping through a hole in the chassis. The manual has the adjustment procedure, but here's a summary:

1. First make sure the free flow pump pressure is set to 9 BAR. The procedure for doing this is also in the manual. It involves loosening the lock nut on the bypass valve on the right side of the pump, running the pump without the portafilter in place (which is called "free flow"), adjusting the bypass valve until the free flow pressure is 9 BAR, then tightening the lock nut.

2. Next run the pump at free flow for about 30 seconds, then turn it off. The pressure should rise from 9 BAR to a maximum of 12 BAR while the boiler is reheating, then slowly decrease. If the reheating pressure doesn't reach 12 BAR, or if it exceeds 12 BAR, you need to adjust the expansion valve.

3. To adjust the expansion valve, remove the right side panel so you can see the body of the expansion valve (see the CAUTION below for the reason.) Then use a pair of pliers with electrical tape on the jaws so you don't mar the brass. Grab the portion of the lower expansion valve fitting that's projecting into the drain box. Turn it left to lower the max pressure or turn it right to increase the max pressure.

CAUTION: Make sure only the lower part of the expansion valve moves when you adjust it. If you feel significant resistance or it looks like entire body of the expansion valve is moving, STOP (this is why you removed the right side panel -- to watch the expansion valve as you turn it.) If you keep turning you may twist the copper pipe that connects the expansion valve to the boiler. This can happen if the lower portion of the expansion valve is stuck to the threads of the expansion valve by scale. If that happens, grab the upper part of the expansion valve with a wrench so you can keep the valve from turning as you try to loosen the lower fitting.

maki

#7: Post by maki »

on my Linea Classic it's 6-13 bar cycles for brew boiler.
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maccompatible

#8: Post by maccompatible »

AssafL wrote:if the pressure oscillates 9-12 bar it seems that the heating element does turn off. Otherwise it will go up to 12 and stay there.
That makes a lot of sense. This is all very new to me, so I appreciate you all bearing with me as I learn.
AssafL wrote:What does the temp reading show?
It's staying exactly where it's set. I'm using a darker coffee right now and have it set to 197, where it has stayed no problem. It also seems to be causing no issues in making espresso, giving tea water, or steaming milk. The only thing I notice is that it SOUNDS like it's warming up all day. Like the soft boiling water noise it makes when adjusting the temperature up 5 degrees. Except it never stops..
Peppersass wrote:You should make sure the expansion valve is properly adjusted.
Could the expansion valve be causing these issues? What would an improperly adjusted expansion valve look like?
"Wait. People drink coffee just for the caffeine??"
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Wattbe

#9: Post by Wattbe »

I experienced a similar problem with my 18 month old GS/3 in that it began making a constant heating 'fizzz' noise. Everything else seemed normal. I ended up replacing the heating element in the steam boiler which solved the problem - it's now quiet again.
When I removed the old element, it did have some scale on it, which I believe was the cause of the noise. I fitted the new element anyway but cleaned up and descaled the original, which I've kept as a spare.
On a separate note, my brew gauge indicates between 6 and 12 bar when idle, so I think that's normal.

All the best,

Ben

maccompatible

#10: Post by maccompatible »

Wattbe wrote:I experienced a similar problem with my 18 month old GS/3 in that it began making a constant heating 'fizzz' noise. Everything else seemed normal. I ended up replacing the heating element in the steam boiler which solved the problem - it's now quiet again.
I just found and read through the thread you posted when it happened. If I didn't know better I'd swear you were describing MY problem. Newer GS3, constant fizz noise, DEFINITELY coming from the steam boiler (the sound stops when lowering the temp within 10 seconds), etc.
It's odd because I know for a fact my initial problem was the vacuum breaker and I don't remember it doing this before repairing it. Now the vacuum breaker is forming a nice tight seal with none of the previous symptoms (sputtering drips into the drip tray, constantly refilling itself with water), but I have this issue now.

Looks like I'll be calling LM again to figure out what the heck is going on. If it's scale like it was in your case, I'm gonna have to figure out WHY. My steam boiler is set to 255°F to get 1.5 bars of pressure, not even really that high. And I specifically mix and use the Barista Hustle water recipe (starting from distilled) to avoid scale issues.
"Wait. People drink coffee just for the caffeine??"
LMWDP #628