# La Marzocco GS/3 MP boiler pressure dropping when idling.



## wattbe (Nov 24, 2015)

Hi there

I've owned my GS/3 for almost a year now and it's been great.

I noticed the other day though, that instead of the brew pressure gauge indicating between 6-12 bar when idling, it was down to below 3. I've never seen it that low before and suspected a small leak somewhere within the brew plumbing.

As I was taking the side panels off to investigate, I could hear a quiet, intermittent popping sound coming from up inside the group head behind the shower screen. I've checked for small leaks inside the machine and there's no visible or tactile sign of a leak.

The OPV is working correctly and isn't leaking.

The group head is dry but emits those intermittent, tiny pops which sound similar to the vacuum breaker if it doesn't seal perfectly and needs a service.

I suspected that the conical valve might need a service and ordered the only 2 O rings on the valve.

I've removed the top part of the group and all of the washers but when it comes the lifting the conical valve up out of the group, it moves up about 5mm but then I can't get it to come off. I've applied as much force as I dare, to the point of using two wrenches as leverage but it just wont budge any further.

I've referenced the parts diagram and there's no locking part.

I then reassembled everything and bled the group and my wiggling and pulling on the conical valve seems to have helped somewhat. It's not idling as low as 2 bar, now closer to 6 which is still slightly lower than it's been for a year but definitely an improvement on yesterday.

Has anyone serviced the group on the newer MP's that could offer any advice on how to remove the conical valve?

The other culprit is one or more of the check valves not sealing properly but that's just a wild guess!

Any advice is gratefully received!

Cheers,

Ben


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## DavecUK (Aug 6, 2013)

Your location, water type used, is it still under warranty (owned for less than a year)?


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## wattbe (Nov 24, 2015)

Hi Dave,

I'm just north of London and it's only ever been used with Volvic. It's still within warranty, just. I've spoken with LM and they said that it sounds normal.

I'll be speaking with them today to follow up.

It's definitely not normal as it's never behaved in this way over the last 11 months.

There's 3 check valves between the pump outlet and the brew boiler. I gave each one a few taps with a spanner in case one hadn't reseated correctly and was allowing a small amount of reverse flow.

It may be a coincidence but yesterday evening and this morning, it's been holding a higher pressure while idling (around 6-7 bar). This is better than the sub 3 bar but not as quite as high as it normally would be (averaging around 8-9 bar).

For anyone not familiar with the GS3, one of the brew manometers indicates the pressure within the brew boiler. With the pump running, it'll show pump output pressure but when the machine is just sitting, it reflects the pressure inside the boiler which is a result of the thermal expansion of the water as it's heated within a sealed system.

I'm not sure if the improvement was a result of the extra movement of the conical valve as I tried to remove it, causing the o rings to reseat correctly, or from the check valves reseating.

Id really like to know how to fully remove the conical valve to service the o rings.

Very much open to suggestions.

Cheers,

Ben


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## wattbe (Nov 24, 2015)

Here's the expanded view of the conical valve. After removing the upper parts, I was left with part 11 sitting in its valve seat within the group. I could raise it 5mm or so but then it wouldn't budge. It's the lower two o rings I'd like to look at/service.


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## DavecUK (Aug 6, 2013)

If it's still under warranty, don't bugger around with it. Most manufacturers/Reteailers I get involved with have a 2 year warranty on their espresso machines...LM probably has a 2 year one as well. I would just register the issue with them, keep copies of communications and perhaps take some video of the problem. In this way LM can't say you introduced the problem.

It does sound like there is a slow leak and you are correct depending on where the manometer takes off there is the expansion of fresh water causing a pressure increase. This can let by from a number of areas, expansion valve, 1 way valve, group valve. Usually this happens for a number of reasons, lime scale, contaminants, debris, wear of a seal. your machine is quite new, so I would have thought it's one of the first 3.

This of course makes the assumption that the seal on the GS3 can't be damaged by closing the group valve too hard...although If I were designing such a mechanism, I would make sure that it can't be damaged that way and I imagine they would have done the same..

P.S. I should add that it's quite common when machines age for this hydraulic pressure on heating to gradually let up as only a tiny tiny amount needs to leaks for the pressure to drop to zero (waters not very compressible). Any machines I get involved in the design of, I actually design out the issue to avoid any problems especially with E61 machines. I would Imagine LM may have done the same. So unless the leakage is excessive, it may never cause a problem. If you find you are running the pump and there is a bit of a long delay getting water out (or a long hold at a lower than normal pressure), it might indicate the brew boiler level being way too low...then you risk heating element exposure and thermal sensors not being immersed properly.


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## wattbe (Nov 24, 2015)

Hi Dave,

Thanks for the response. You're exactly right regarding the 3 possible causes. I've checked the expansion valve and that's working correctly which leaves either the group or check valves. I'm inclined to think it's the group valve as I can hear a slight popping noise coming from behind the shower screen which, from my understanding, would be indicative of a very slight leak?

You're also correct in saying that the seal can't be damaged by closing the group too hard, it has a mechanical stop which prevents that.

The issue is in its infancy and doesn't stop me from using the machine, but I'm concerned that, when I leave it for longer periods of time without use, the gradual pressure drop will indeed cause the water level to drop and expose the element. At this stage, that would take a long time as the leak is very small and the boiler is quite large, but if it suddenly got worse, it could become an issue.

LM said pretty much exactly what you said regarding the slight pressure drop as the machine ages which is why I think they initially dismissed it as normal. However, this hasn't been a gradual drop over many months. On Wednesday it was idling normally at around 9 bar and on Thursday it was down to nearly 2 bar. This to me indicates that something has suddenly happened.

I'll post back once I have more info from LM.

Thabks for the info.


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## DavecUK (Aug 6, 2013)

I think if it's a sudden difference then your right to be a little less relaxed. The heating elements won't be exposed until the level drops a lot but that would give more obvious symptoms.


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## Scotford (Apr 24, 2014)

On commercial LM machines the pressure gauges flit across the place as they take readings from different parts of the machine and show that. The instant you do something with it it comes back to brew or steam pressure reading though.

Might be the same.


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