New to me La Marzocco GS/3: Steam boiler not heating, odd pump noise

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

#1: Post by daynejones »

Well a GS/3 MP finally came up on the used market and I took the plunge.

It was part of a fleet of machines that were leased to companies in the Bay Area so it was built in 2007 and has been well used and maintained since. I've been using it as is for a while and it has been a dream. Well the steam boiler stopped heating up, intermittently at first, and now it won't come on at all so I've finally opened her up.

She's actually in really good shape, no water incursion in the brain box, hardly any signs of rust or mineral buildup, just needs a bit of TLC.

The current list of issues are as follows:

1. Steam boiler won't turn on.
Swapping the thermostats did nothing and both thermostats show 0.1 ohm resistance (although one of them shows higher resistance at first... weird). Swapping the SSRs moves the problem to the other boiler. Great. I have a new SSR and a new thermostat (for good measure) coming in the mail.

2. Now that I have the machine back together, the rotary pump makes a horrible buzzing sound. The shot still pulls with proper pressure though.
To me, it feels like not enough water or too much back pressure. I have it plumbed in from my kitchen sink with no filter since Oakland water is ostensibly pretty good for espresso, although I do have a 35 psi regulator inline. Curious that it started after I got into the machine.

The only new thing I noticed was a little black residue, like oxide of some sort in both the tea dispenser water and the water from the brew head. I inspected the 2 easy to find check valves and they look good and I drained both boilers just to be safe.

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#2: Post by Peppersass »

The GS/3 MP didn't exist in 2007. Did you mean 2017? That would make more sense, given the excellent condition of the machine.

Sounds like you nailed the heating problem. Good work.

On the pump noise, first thing I'd do is grab the braided pump input hose and see if that changes the noise. The position of the hose on its way from the regulator might have changed when you moved the machine to remove the covers and pull out the brain box, and it might be rubbing against something that's rattling. If that doesn't change the noise, grab the output hose. It may have moved slightly and is rubbing against something inside the front of the machine.

While you're at it, grab the pump. If the noise changes or stops, then it's possible something in the mounting system is loose. Make sure the clamps that connect the pump to the motor are screwed on tight. Also check that the bolts that secure the motor to the chassis are tightened.

If that doesn't solve the problem, you could disconnect the pump from the motor and see if the noise is coming from the motor. If so, it's probably a bad bearing. Haven't ever heard of that happening in a GS/3, but it's possible.

Also check all of the bolts on the four support brackets -- top and bottom. One or more might have worked loose.

If all that doesn't reveal the source of the problem, then it could be that the pump bearings or vanes are worn out and need to be replaced. I think that can be done without replacing the entire motor, but I'm not sure the parts are easily available.

daynejones (original poster)

#3: Post by daynejones (original poster) »

Well I don't know where I got 2007 from then. I suppose the "Data: 09/14" here means 2014.

I played around with the pump, hoses, and mounts while running the pump and the noise barely changes. It's clearly coming from the inside of the pump.

I can pull the pump and take a look inside but I don't know if that's even possible. I actually have a spare fluid-o-tech sitting in my Spaziale. It is bigger than this one but it may fit well enough for a test.

daynejones (original poster)

#4: Post by daynejones (original poster) »

Well, removing the pump and running the motor proves that it's the pump making the noise... Sounds like rebuilding is not really feasible so I'm in the market for a new pump!

I'm curious how the issue just popped up now. I ran the pump dry for a few seconds by accident while working on it, I wonder if that was the last straw.

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#5: Post by Peppersass »

Yes, it was built in September 2014.

It's generally not good to run the pump when it's dry, but I don't think running for a few seconds would destroy it. It must have been on the verge. Not too surprising if the machine saw 7-8 years of cafe use.

Are you sure the pump can't be disassembled? I thought FOT rotary pumps could be, but maybe I'm mistaken.

What happens pressure-wise with that pump? Are you getting 9 BAR?

It's a long shot, but if your bypass valve spring is broken it might be what's making the noise. Easy enough to unscrew to check and replace if needed.

daynejones (original poster)

#6: Post by daynejones (original poster) »

I can find videos of people dismantling them but none of them rebuilding or repairing.

I was getting 9 BAR before I took it out. I found little metallic shavings in the water I dumped out of it. Now that it's back in, the noise is different and it's not getting up to 9. Seems like it's toast.

I've got a local guy with replacement pumps so I'll post an update once I get the new pump in.

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#7: Post by Peppersass »

Yikes -- metal shavings! Hope they didn't get into the rest of the machine.

Definitely time to replace that pump. I'd drain and flush the boilers a few times after the new pump is installed, and carefully inspect the drained water for any metal shavings.

daynejones (original poster)

#8: Post by daynejones (original poster) »

Great point, although I'm not 100% sure I know how to do that properly. The way I learned to drain the brew boiler is (1) remove the expansion valve, then (2) unscrew the bleed screw in the brew head. As for the steam boiler, the easy part is opening the valve at the bottom, the hard part is doing without making a mess. Does that sound about right to you?

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#9: Post by Peppersass »


For the coffee boiler, you don't have to completely remove the expansion valve. Just unscrew it until a few drops of water emerge. Then unscrew the bleed screw. That'll increase the flow. Continue unscrewing the expansion valve, which will increase the flow. Stop turning when the flow rate doesn't increase anymore.

I drain the steam boiler as follows:

- Obtain a 1/2" brass hose barb, a 1/2" ID brass female-female adapter* and a six foot length of 5/8" OD x 1/2" ID plastic tubing. I got these items at my local hardware store. (* The female-female brass adapter screws onto the threaded portion of the 1/2" brass hose barb. The barb and the ID of the threaded portion are 1/2", but the OD of the threaded portion is 5/8". I'm not sure whether the correct female-female brass adapter is measured by the ID or OD of the male adapter it screws on to. The diameter of the internal threaded portion needs to be 5/8" in order to screw onto the threaded portion of the hose barb and drain valve.)

- Turn off the machine and let it cool. Usually a good idea to turn off the main switch in the back and unplug the machine.

- Grab the drain valve body with a wrench and use anther wrench to remove the brass cap. This will prevent unscrewing the drain valve from the boiler or the fitting that connects the drain valve to the boiler. As you remove the brass cap, take care not to lose the dome-shaped slug inside. Note the orientation of the slug. The rounded part fits into the opening in the drain valve and the flat end fits into the drain cap.

- Screw the hose barb and female-female adapter together. Finger tight is probably OK, but no harm in using a pair of wrenches to tighten.

- Screw the hose barb/adapter assembly onto the drain valve. Tighten by hand -- just finger tight is best. Do not tighten with a wrench. I'm pretty sure the drain valve has BSPP threads, while female-female adapters you can get from local hardware stores will most likely have NPT threads. The threads will screw together only partway. If you try to go beyond the first sign of resistance, you'll damage the threads. Finger tight is OK because there will be no pressure in the line when you drain the steam boiler. The joint just has to be tight enough to avoid leaking, which isn't all that tight.

- Slip one end of the plastic hose onto the drain barb. It should be a snug fit -- not loose and not so tight that you have to fight to get the hose on. Run the hose over the counter and towards the floor. Put the other end in a bucket or container that can hold at least one gallon of liquid.

- Open the drain valve using the black plastic handle of the ball valve. It only turns 1/4 of a turn. Don't force it beyond that or the valve may be damaged.

- Water will drain out of the boiler through the hose into the container. When the flow stops, gently lift the right side of the machine so the remaining water can drain out of the boiler.

- Close the drain valve. Again, don't force it beyond 1/4 turn.

- Pull the hose off the barb and unscrew the barb/adapter assembly. Put the dome-shaped slug in the brass cap (flat side facing the cap) and screw the cap onto the drain valve, taking care to make sure the slug is oriented so as to fit evenly into the hole in the drain valve. Use two wrenches to tighten the brass cap.

- Re-check to make sure the ball valve is closed before turning on the machine.

daynejones (original poster)

#10: Post by daynejones (original poster) »

Well I went ahead and ordered a brand new pump directly from fluid-o-tech. Kim Ciccarello was a huge help. She can be reached directly at 860-276-9270 ext 100. They only had the brass version though. $106!

Here is a pic of some of the goodies that came out of the old pump.

And the pump installed. I'm a little concerned that something may have made its way upstream in the system but I drained both boilers as a preventative measure.

So I pulled lots of tasty shots for a couple days before a new issue popped up. It looks like the safety valve is stuck in the open position. This leads to the safety valve cover filling with water and overflowing in the time it takes to pull a shot. It also seems to hinder steam pressure too, although I'm not sure why this is the case.

Next step for me is to remove and inspect the safety valve but I need to find a socket big and deep enough to do the job. Will report back. Thanks again for your help.