Replacing steam boiler seals on the La Marzocco GS/3

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Peppersass
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#1: Post by Peppersass »

IMPORTANT: GS/3 owners who read this post should not panic! To my knowledge, failure of the GS/3 steam boiler seals is extremely rare. La Marzocco has sold thousands of these machines, and I know of only four instances where the steam boiler seals leaked. Three of the machines were from the infamous batch known as the "fire sale" machines, manufactured circa 2009 with serial numbers in the 500-700 range, which may have been stored improperly in a distributor's warehouse. I don't yet know if the fourth machine is from the fire sale batch. It's the subject of this post by espresso-shots.

I've been meaning to do this post for three years, but never found the time. It's really a follow-up to my post about the logic board in my GS/3 getting fried by water that leaked into the brain box. In that post I had speculated that vapor leaking from the old-style vacuum breaker had condensed and formed the water that ultimately contaminated the logic board. But while that is definitely a possible source of water incursion into the brain box, eventually I discovered that both steam boiler seals were leaking. Various CPU anomalies that occurred from the day the machine was first installed convinced me that the seals had always leaked, but the leaks were very small at the beginning and only happened on infrequent occasions when the machine was turned off and cold.

I dont' have time at the moment to fill in the complete story about replacing the seals, but I wanted to post at least the photos and some captions in order to help espresso-shots and anyone else facing this problem.

WARNING: The procedure described herein must only be done when the machine is turned off, unplugged and both boilers are drained. Improper installation of new steam boiler seals could result in damage or injury, so this is a procedure that should be done by qualified personnel, preferrably your authorized La Marzocco dealer. Otherwise, you undertake it at your own risk. [END OF DISCLAIMER]

Removing heating element from left side of steam boiler. Note black seal on triangular plate:



Close-up of left-side steam boiler seal. Note deformation at top:



Steam boiler opening. Looks like lubricant was applied to the seal and it leached away, but I'm not sure:



Old (damaged) seal on left, new seal on right. Hard to tell if they're made of the same material or if the old seal was originally flat or round:



A better look at corrosion around the base of the heater:



Left side seal. It's deformed and cracked:



It's harder to get the right-side plate off because there's a lot of tubing in the way. Here I'm starting to remove the steam boiler fill tube from the solenoid side:



And from the boiler side:



The tubes that connect the heat exchanger to the stainless steel block must be removed. Here I've loosened the nut at the block end of one of the tubes and have slid the nut toward the steam boiler:



Then I unscrewed the nut at the boiler end or the tube and pulled it out of the block and the triangular plate. I've also loosened the nut at the block end of the other tube:



Here I'm slowly and gently working the heat exchanger out of the steam boiler. Extra care must be taken not to damage the tubing:



And here's the heat exchanger:



From this angle there appears to be less corrosion on the plate and the seal looks better:



But that's just the angle of the photo. Check this one out:



And here you can see that the right-side seal failed, too:




But the inside of the steam boiler looks great. No scale!



Cleaned up the heat exchanger in distilled vinegar and gently polished with a scrubbie:



Did the best I could to clean up the plate, especially the area where the seal sits:



Hear's the heating element and plate cleaned up:



And with the new seal in place:


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FotonDrv
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#2: Post by FotonDrv »

Dick, that is a nice Posting, very clear and informative!

Do you think different metals and their chemical interactions are causing the problem you have beautifully described?

Good work!
Stephen
That Light at the End of the Tunnel is actually a train

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AssafL
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#3: Post by AssafL »

Dick - Great post - I had to replace mine as well.

1. My machine was indeed from the so called Franke "fire sale" era.

2. I did remove the heaters before to swap with 220V heaters (moved to Israel) - Since the 220V ones were supplied with new Viton O-rings they are rather new.

3. The O-ring for the heat exchanger failed after the check valve between the boiler and the hot water mixer failed and allowed full plumbed in pressure to get to the steam boiler. It then started to leak and had to be replaced.

A few comments:
1. The O-rings have to be Viton. Regular O-rings disintegrate at over 70C and will perish quickly in that environment.
2. My seals looked the same (triangular cross section and mushy textured). I think these have to be replaced at 4-5 year intervals. Even Viton loses its ability to seal and the computer board mounted below is so expensive...
3. Inside of boilers looks pristine. Pretty amazing for a machine that has been at boiling point for about 5 years...
Scraping away (slowly) at the tyranny of biases and dogma.

OldNuc
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#4: Post by OldNuc »

Look at this chart and select the proper material for the environment.

http://www.mcmaster.com/#o-rings/=v0ymrd

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Peppersass (original poster)
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#5: Post by Peppersass (original poster) »

AssafL wrote: 3. The O-ring for the heat exchanger failed after the check valve between the boiler and the hot water mixer failed and allowed full plumbed in pressure to get to the steam boiler. It then started to leak and had to be replaced.
Scary that a check valve is all that stands in the way of such a failure. But I would have expected the steam boiler OPV to trip and prevent the boiler from overfilling and ruining the seal. Perhaps it only takes a brief and moderate over-pressure situation to blow the seals. If so, maybe the OPV sensitivity and trigger speed needs to be reconsidered.

FWIW, prior to the complete failure of my logic board there were a couple of instances where the steam boiler overfilled and popped the OPV. A level probe failure like this seems to be a pretty common symptom of water getting to the logic board. That's been reported here a few times. What I don't know is whether those initial probe failures in my machine were caused by water leaking from the seals, or whether they were caused by condensed vapor from a stuck vacuum breaker valve. Either way, the overfilling/overpressure may well have been the cause of the seal failures or may have made them worse.

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AssafL
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#6: Post by AssafL »

Peppersass wrote:Scary that a check valve is all that stands in the way of such a failure.
Tell me about it. In a plumbed in machine, if that check valve fails - it fails open and water starts flowing out of the OPV (steam everywhere - quite a sight). I think it is the main fault scenario that worries La Marzocco support for plumbed in machines that do not plumb in their drain.

If you look at the newer diagrams you'll see that they added an additional (redundant) check valve on that line. I guess that check valve caused problems for more people (It does sit on water at 212 or above so it will probably fail before other check valves). I replaced that line and updated it to the new configuration (see below right).

Peppersass wrote:Either way, the overfilling/overpressure may well have been the cause of the seal failures or may have made them worse.


IMHO - I don't think the OPV set point was the cause. I think a 5 year old seal loses its elasticity, at which point it is a ticking time bomb. If it wasn't for the check valve failing, perhaps it would have taken it an additional few months to fail.

There are different classes of Viton (fluoroelastomer O-ring) and perhaps there are better ones with a longer life in these conditions.

BTW - In Israel, a local Espresso Machine repair guy gave me a few paper seals like they use in cars, cut to the shape of the heater plates. They are installed in a addition to the Viton o-ring. Aftermarket espresso machine maintenance stuff.
Scraping away (slowly) at the tyranny of biases and dogma.

OldNuc
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#7: Post by OldNuc »

Neither Viton or Buna-N are rated for a hot steam or water environment. The extrude out and fail. The Aflas material is the best choice at the lowest cost, PTFE is the proper pick but the cost of those o-rings is prohibitive. Continued use of an improper material will require continuing periodic replacement on a time frame short enough to schedule replacement before failure. Flat vegetable fiber gaskets is probably a better choice than Viton or Buna-N

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JohnB.
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#8: Post by JohnB. »

I'm surprised that LM isn't using a flat teflon gasket on the heating element plate. Based on my experience with the Speedster they seem to hold up indefinitely. I pull the steam boiler element out for scale inspection every 12-18 months. Just had it out a few weeks ago & the original gasket still looked fine after 5 years.
LMWDP 267

OldNuc
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#9: Post by OldNuc »

They built the element and boiler face for an o-ring type seal. There is probably inadequate surface area for a flat gasket to reliably seal long term and add to that that PTFE will cold flow over time and you end up with a very slow leak. There are a couple of o-ring materials that would last a couple of normal lifetimes and even allow for a removal and replace without o-ring replacement but the drawback is they are expensive.

The periodic opening of the boiler effectively re-torques that flat gasket upon reassembly so no slow leakage due to loss of torque on the gasket.

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JohnB.
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#10: Post by JohnB. »

As I said I've had no leaks in 5 years & I've had the element out several times so I'm sold on the Teflon gaskets, especially after seeing this thread! The o'rings compress over time also so I'd say checking the nuts every once in a while to make sure everything is snug wouldn't be a bad idea. Unlike the various rubber options the teflon isn't going to get brittle & crack.
LMWDP 267

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