I bought a Mara X from BB nearly 3 years back and today when I turned it on as normal, the boiler pressure built up without any control and exceeded 3 bar so much that the needle passed 3 o'clock and steam pressure was released at the bottom of the machine. I immediately shut the machine off and drained the boiler but have left the machine off since. I last descaled the machine a year ago and since then have exclusively used Osmio Zero water through it. I usually have milk drinks so when I shut the machine off I always purge 200ml from the boiler so it's not sitting with overly mineralised water. Has anyone come across this problem before and do you have any suggestions on what to try to fix it? I've taken it apart to do the OPV re-route but I'm not super familiar with the innards of the machines so layman's advice to start would be appreciated!

@"pandabear"#p64305 It's possible the temperature sensor has developed a fault and that might be the first thing to check/replace. especially if readings are erratic.

Thanks for the swift reply Dave. I actually flicked between mode 0 (steam if I'm right, I'm on a V1 machine) and back to mode 1 (coffee mode ie. walk up and pull my shot) and it seems to have stabilised, oddly. The machine pressured up past 3 bar when I reset the mode to coffee mode but then has dropped back to 1.5 bar since and stayed there with the pump going occasionally. Just ran a backflush for 20 seconds, pump at 9 bar and pressure hasn't gone mental since (activated the boiler a few times, went up to 2 then pump activated momentarily and now idling around 1.5). Is there an easy way to test the temperature sensor since I have the top off the machine off at the moment, or am I better off leaving everything as is for now?

Side question - is idling between 1.5 - 2 bar actually normal? What I keep seeing now I'm Googling is that the pressure should rest between 0.5 and 0.75 typically?

> @"pandabear"#p64314 Is there an easy way to test the temperature sensor since I have the top off the machine off at the moment, or am I better off leaving everything as is for now? No, and wobble the wires around too much is a sure way of breaking it.

> @"pandabear"#p64317 is idling between 1.5 - 2 bar actually normal? You can see how my machine is idling in these two time-lapse videos below. This is coffee priority with temp setting 0 (the lowest). I think idling between 1.5 and 2 bar is too high, at least compared to my machine (same version and about the same age as yours). This is starting the machine from cold: https://www.youtube.com/watch?v=5DOTP7owHZg&ab_channel And this is idling after a shot: https://www.youtube.com/watch?v=-a5u3XuVLm4&ab_channel

@"Doram"#p64424 Looks fine to me?

> @"DavecUK"#p64425 [Doram](https://coffeetime.freeflarum.com/d/2546-mara-x-pressure-builds-continuously-before-venting-at-base/6) Looks fine to me? Yes, this is my machine and it's fine. I uploaded the videos for @"pandabear"#645, because his machine is idling between 1.5 to 2 bar and he asked if this was normal, so this was just for his reference.

Confirming my suspicions that the temp has been off a bit for a while and this issue is probably a culmination of that. The issue happened again earlier after I let the machine idle for over an hour. Slowly built up and then tripped over. Wondering if I should look at the steam temperature probe before I check anything else. Seen another person has some loose wiring at the bottom of the boiler too so might up taking off the casing and checking all wires/connections properly.

Edit: should have said check the temp probe first as I've also been advise to check/swap the pressure stat (is that the actual dial on the front?)

@"pandabear"#p64428 MaraX doesn't have a pressurestat. As I said before, change the temp probe. It could be the one in the HX circuit, but more likely the one on the top of the boiler. https://coffeeequipmentreviews.wordpress.com/2020/03/10/lelit-marax-review-in-progress/#temperature **It's worth mentioning the temp probe on the top of the boiler is a combined temperature and Level probe!** There should be an extra boiler plug on the top that's not used, if so undo it. Then buy a separate level and temperature probe, The combined one can be more expensive. The wiring is self explanatory.

Mara X pressure builds continuously before venting at base

pandabear

Yes, I meant it behaves the same at low temp and middle temp in coffee mode. I’ll try another time lapse as suggested tomorrow morning and upload. I’m going to have another look at the level probe tonight after reading another thread here and checking Lelit’s suggestion of having ~15mm of the metal clear at the bottom - I think mine had about half that when I checked a couple of weeks ago. The inner plastic also rises at the top a bit so I’ll trim it all down to size to make doubley sure.

DavecUK

Just remember there are 2 temp sensors for the brewing side, one in the thermosyphon loop and one on the boiler….if either is playing up, this could happen. It’s also possibly that the thermosyphon loop might be stalling a little if there is a leak in the seal?

pandabear

So timelapse from startup this time for 1.5 hours. Watch there to show time elapsing. I couldn’t slow it down unfortunately though. Same issue persists.

I followed this by pulling a shot and then leaving the machine to see what it did. After an hour or so of being idle after pulling the shot, the machine temperature light started blinking without returning to a solid on state. The pressure remained fluctuating in the same pattern. That made me think something electrical is possibly at fault/also at fault? I’ve read that the gicar and the SSR can be causes?

DavecUK

pandabear Probably a temp sensor

pandabear

@DavecUK okay, would you suggest putting the old one from the top at the bottom? Is that the logical sequence to try?

DavecUK

pandabear I don’t like buggering around with them too much as the wires can break, but yes…try that first as it’s unlikely both sensors have gone bad at once.

pandabear

So as per the other thread I’ve removed the bottom probe and descaled it (minimal scale). The water that I removed from the thermosyphon was very dirty though and the inside of the boiler looks similar from what I could see. I’m going to run a full Puly descale tomorrow.

Will I need to empty the boiler and thermosyphon again after descale to get all the crud/scale out? Or should that all flow out with the descale procedure? If I do need to, how can I do that on the main boiler given it’s not super accessible?

StevenG91

pandabear

Just run a descale. There’s a detailed video here

pandabear

After cleaning the bottom HX temp probe it’s made no difference.

Swapped the bottom HX probe for the original top boiler probe and that’s made zero difference either. I suppose both original probes could be faulty… What would the chances be? Both are marked “HT 03/21”. Unsure if they were part of the faulty batch I’ve read people chat about. Either that or some erroneous scale problem (got the Puly descaler just now so will try that tonight/over the weekend, not holding out hope though) or something completely different like gicar malfunction.

DavecUK

Not likely both would be faulty?

pandabear

I suppose it’s possible that the bottom one has been faulty for a while and it’s gone unnoticed until now (says a lot about my palate if so!). I managed to slash my knuckle right open undoing the probe yesterday too, the force carried my hand the sheet metal! I’m having loads of fun with this 😅

DavecUK

pandabear I suppose that is possible f it’s been a bit iffy for a while and you didn’t notice now another has gone faulty and it’s become more obvious?

pandabear

I think the machine is behaving normally now. Did a full descale and now my Mara settles between 0.75 and 1.25. I can hear that the boiler is ticking over every so often rather than coming on full pelt for a few seconds every 30 seconds or so which was the case when the manometer oscillated between 1.5 and 2 bar.

No idea if the descale process did the trick in isolation, or whether cycling the machine all those times helped reset something. As it stands I have a new thermo probe at the top of the machine and the probe that was at the top is now at the bottom.

Will continue to monitor and see how I go. Thank you @DavecUK @StevenG91 @Doram for your support!

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