La Marzocco GS/3 Part Failure And Minor Maintenance - Page 2

#11: Post by **Peppersass** » April 11th, 2018, 12:17 am

The OPV will close once the pressure drops below its threshold. However, if a tube pops off the tee, enough steam would come out and condense as water inside the machine to be a danger to the logic board.

And that's not what you really have to worry about. It isn't likely that too much steam pressure will build up in the steam boiler. Both the temperature probe and the thermostatic breaker would have to fail.

A rare but more likely scenario is boiler overfill due to the wire connector coming off the level probe, failure of the probe or failure of the wire. In that case, the boiler fills up and pressure builds until the OPV opens. Water will continue to spray out of the OPV until the cause of the overfill is fixed or the machine is turned off. If a tube blows off the tee, the inside of the machine will be drenched,

This can also happen due to water contamination of the logic board due to an unrelated leak. Happened in my machine more than once until I nailed the cause of the leak. However, that was when I had the old vacuum breaker. No tee, so the water went into the drain box. The tube didn't come off the OPV can nipple or the drain box nipple, but those are very tight fits.

After pondering this I'm considering using some kind of plastic epoxy on the tube connections at the tee to permanently secure them. But I can't see a way to secure the connection at the vacuum breaker without making it unserviceable. Have to hope the open path to the drain box would provide enough pressure relief to prevent blowing that tube off.

#12: Post by **Peppersass** » April 11th, 2018, 12:43 am

wholemilklatte wrote:@peppersass, how did you cover the holes in the frame? I was going to plug them with silicone while i was in there but decided not to do it right away and figure out maybe a better way, especially given the heat and proximity to the wiring and boiler.

J-B Weld WaterWeld

It's a putty-like epoxy for plumbing applications. You pinch off a piece, roll it around to activate the hardener, then mold it into place. It hardens to a waterproof ceramic-like consistency with a temp rating up to 300F.

I had pulled out the brain box, so I was able to push a blob of putty into the hole and press it with my finger from below to spread it out around the bottom side of the hole. Then I held it in place from below and spread the putty around the top side of the hole.

#13: Post by **AssafL** » April 11th, 2018, 2:17 am

Have you guys considered using hose spring clamps? They are very strong, easy to remove for servicing. And so very cheap.

(I acquired the retrofit vacuum breaker with the vent to a front mounted nipple so no worries there).

BTW - if the failure mechanism causes the autofill solenoid to remain open eventually water flows out from the OPV. The heater tries to heat the water but cannot keep up and eventually all the steam gets displaced by water. It is the worst sort of problem since if the machine isn't plumbed out - the water will overflow the drain box and over time can cause water damage.

April 11th, 2018, 3:57 pm

I was thinking about those too @AssafL- i think you're right, they'd probably work well in this case

#15: Post by **chrisvarghese** » April 11th, 2018, 6:02 pm

wholemilklatte wrote:The expansion valve controls over pressure for the coffee boiler - and is the one you're talking about, it's a brass piece connected to a copper pipe and exits on the right side of the drip plate. It tends to be configured to allow water to exit at ~12bar of pressure although it may drip occasionally, especially as the boiler is coming up to pressure.

I don't think it needs to be replaced unless you're having a problem with it. I also picked up a new one for my machine but haven't replaced it as the one on the machine now works perfectly. Having one on hand is nice through so that in the event of a problem i won't have any downtime in the future.

The OPV on the steam boiler (which is what we were talking about) is located inside of the machine. It actually sits in a small metal can and is connected to the steam boiler by a short length of copper pipe. It sits sort of above the motor and in between the two boilers. My motor is external to the machine so it's easier to access but in general to get to it you'd need to pull at least the right side panel, the top panel and probably the back of the machine.

You could try draining the coffee boiler and see if your expansion valve needs replacing as part of that - although i'd doubt it. I think it's good practice to drain the coffee boiler periodically (i don't know the right frequency or how important it is). LM recommended to me to drain the steam boiler every 3 months. The steam boiler is a difference situation from the coffee boiler due to the potential for the buildup of scale, and increasing concentration of minerals in the water that's present. The coffee boiler is fully saturated so you don't have that same problem.

I drained my steam boiler last weekend for the first time after replacing my ball valve and it's super easy when everything's working properly (go figure )

Once the machine cooled sufficiently i pulled the left side, removed the cap from the ball valve, hooked up a hose routed into the sink, and opened the ball valve. ~30 seconds later the boiler was empty, i rocked the machine a little to get the last of the water, closed the valve, put the cap back on and powered it up. If you ignore the cooling and heating cycle the whole thing takes maybe 5 minutes. If the ball valve fails like mine did, it took 4 days and priority shipping

Thanks for that explanation, for some reason, my steam boiler does not have the ball valve. I did buy a replacement ball valve but have not installed it but reading your experience, I might not bother installing it.

What's the best way to drain the coffee boiler?

#16: Post by **AssafL** » April 11th, 2018, 6:15 pm

chrisvarghese wrote: What's the best way to drain the coffee boiler?

Open the expansion valve and let the water cycle.

April 11th, 2018, 7:53 pm

chrisvarghese wrote:my steam boiler does not have the ball valve

That's surprising, are you looking in the right place? It can be difficult to see the actual valve as it gets buried in the cable bundle that runs through there. As you're facing the machine it's behind the left panel on the bottom left side of the steam boiler kind of wedged in the corner.

The order of fittings goes something like:
Steam Boiler -> BSP/1/4" Fitting -> Ball Valve -> Ball Valve Cap

April 12th, 2018, 6:06 pm

Yea I'm pretty sure. I had the whole machine stripped when I was doing my side mounted steam lever mod. You can see the photos and the ball valve missing in some of these photos, here's the link to that article,

DIY La Marzocco GS3 Side Mounted Steam Lever

April 12th, 2018, 8:15 pm

weird, it looks like a slightly different configuration than mine too. There's a cap there, right below the heating element, that looks like the same cap that's on the ball valve on my machine but it seems like it should be sticking out a little further.

It might be good to figure it out the next time you're doing some work in there. I have a feeling you could prop the machine up leaning to the right and it'd be ok. proceed with caution etc etc

I remember seeing your thread last year when you were doing that work, it turned out great!

September 26th, 2018, 12:29 am

So, I kinda kept procrastinating my maintenance and I've managed to get some time now and plan to do some maintenance on my GS3.

I've not had any failure on the OPV or Vac Breaker so not sure if I should bother changing them. Otherwise I was going to do the following,

1) Replace group head gasket
2) Replace shower screen (thinking Pesado Competition shower screen)
3) Rebuild steam valve
4) Drain steam boiler
5) Drain coffee boiler (need to figure out how).

Any other maintenance I should be doing?