La Marzocco Linea Mini Brew Boiler Overheating

Need help with equipment usage or want to share your latest discovery?

#1: Post by oriboaz »

Hi all,

Recently, my Linea Mini's brew boiler has started overheating. When I turn on the machine it sometimes heats the brew group too much. A small bit of water might drip from the brew group, and when I brew, water exiting the group is hissing with steam. After a few seconds of this, the group cools down a bit and functions normally. The overheat switches on top of the brew boiler don't trip or anything like that. This does not happen every time I turn on the machine, but it does too often for me to notice. This can also happen a little time after turning on the machine, e.g. when I run a clean cycle I will find this to sometimes happen.

The brew temperature is set to 92 degrees (both in the app and the temperature wheel). I have played with this setting, but that does not help. This happens even when the steam boiler is off. I have recently replaced both the brew group gasket (H.3.007) and the shower holder seal gasket (L105/A).

Any ideas what might be the problem? Is this something I can (relatively easily) fix myself?



#2: Post by transit »

As I said in this thread Steam coming from grouphead of La Marzocco Linea Mini
I've had this issue for a while (and periodically) probably for two reasons :

- about a year ago in conjunction with problems with the steam boiler. I had the board replaced and solved the problem for a while;
- more recently it happened again and a LM tech told me to do a weird thing that actually worked :
"I can suggest that the cable plugs coming from the coffee boiler thermostat in the black high temp sleeve could be re-crimped."
I did it with pliers, no issues for months.

In my case, the safety thermostats used to trip though.

oriboaz (original poster)

#3: Post by oriboaz (original poster) »

Thanks for the suggestion!
In my case the safety thermostat does not trip at all. The steam boiler cannot be the culprit, as this happens even when I turn it off entirely.

As a first measure, I played with the temperature wheel up and down for about a minute. I read somewhere that the potentionometer may get stuck and this is a possible solution. We'll see if this helps.


#4: Post by agm9 »

I also have this problem with my LM. When first turned on, the group only heats to about 83deg C or so (tested with a meat thermometer which seems to work). After a few flushes it gradually comes up to 94deg. The wheel is set to its mid position of 96.
Then I can pull a shot or two. Without extra flushing they would be very sour.
Then randomly after a shot or two, the brew water overheats and comes out hissing - and obviously measures 100deg. After flushing again it settles back to 94.
A couple of times the machine has refused to heat past the 82 mark. Resetting the two microswitches over top of the group fixes this.
I've yet to get the service people on to this - the machine is at a bach and I have to bring it back home first.

oriboaz (original poster)

#5: Post by oriboaz (original poster) »

I wanted to update that rocking the temperature wheel back and forth seems to have done the trick. The machine is back to functioning normally.