I have a La Pavoni Europiccola from the mid 70's that I bought on ebay. I descaled and cleaned it and have been using it without any problems for the past few weeks. Today I made an americano after lunch again no problems with the machine. But just a few minutes ago I decided to make some kind of milk drink, I turned the machine on II and it started making a loud thumping noise that vibrated everything on the table. I quickly turned off the machine opened the steam wand and when nothing came out took off the boiler cap thinking maybe it was a problem with the pressure. I turned on the machine to II again with the boiler cap off so no pressure would build up and it started thumping again. I turned it off and tried turning it on to I and there was no thumping....so it seems to only happen on II.

Does anyone have any idea what could be causing this? I'm scared to use my machine when it's suddenly making noises like that

I dont know, mine makes some noise when heating up as things expand, a little popping/cracking type of noise, but noting I would call thumping.

Does it do it with the cap off the boiler (not building pressure)?


Perhaps its possesed and doesent care for milk?

Yes it happens with the boiler cap off.

I'm used to the hissing and popping sounds from steam...this thumping noise is louder and lower pitch and begins immediately when I turn on the machine.

It's also just happening suddenly after having used the machine for a while.

Hello:

Have a look inside the boiler with a small flashlight (MiniMag type thingy) and see about the state of the element. It may have developed a crack with water seeping in.

If you cannot see anything, check the continuity and isolation of the element with a tester to see if that is OK.

Then check the resistance across the element, which can be calculated:

W (watts) = V (volts) x A (amps)
You know the voltage and the wattage so you can calculate the amperage.
Then, to find the resistance, you use V (volts) / I (amps) = R (resistance).

If the R value (+/- 10%) is not what you've calculated, there's a problem somewhere.

Good luck,

CIV

Thanks Civ...

I emptied the boiler and took a look inside. Only thing amiss was I saw some pretty big lumps of scale underneath the element and around the intake for the grouphead and sight glass. Looks like leftovers that were too big to completely dissolve when I descaled before...I will have to make another round it seems.

The element itself looked fine, and there wasn't any limestone stuck onto it. I filled the boiler again and tried turning it on while I could see inside with the flashlight and the noise is gone. I don't know if maybe there was something under the base I missed or maybe one of the limestone pebbles was knocking around inside because emptying and refilling the boiler stopped the noise.

I'm going to try descaling again and really letting it soak for a bit this time....if the problem re-appears I'll borrow my dad's multimeter and try checking the wiring...

Hello:

entropyembrace wrote:Thanks Civ...

You're welcome. =-)

entropyembrace wrote:I'm going to try descaling again and really letting it soak for a bit this time....

Carefully ...
Descaling can be a tricky biz.
Acids and brass/copper are not the best of friends.
It's better to do it slowly (no strong acid concentrations) and checking the element's state as you go.

Glad the thumps have gone away.

Cheers,

CIV

The thumping sound may be a cavitation event associated with the element. If there was a crack in the outer sheath it sound be instant pfffft...short circuit and if you had it on a gfi breaker it would throw the gfi and if no breaker it would shock you when you touch the machine.
Cavitation knock is caused by flash boiling at the element and generally happens when there is some steam leak at a seal or fitting.

I have a machine from the 70's as well and mine goes basically the same thing that you are describing (when you first fire it up). It will do it with or without the cap on. It should go away fairly quickly, however, once some pressure is established in the boiler. I would say after 30 to 60 seconds (once the cap is on), but don't quote me on that.

Fire it up and see what happens!

Ray

Hello:

orphanespresso wrote:... may be a cavitation event associated with the element.

Had not thought of that, never seen it happen.

orphanespresso wrote:... a crack in the outer sheath it sound be instant pfffft ...

I agree.
I should have said pin-hole and I guess it also depends on the size of it.
I once had a couple of very small ones with no shorts in my Pavoni Shirley.
But there were small leaks to ground, detected 'by hand', if you will.
There was also quite a bit of 'extra' noise inside the boiler.
Of course, at the time that particular setup had a breaker with no gfi.
This was with the original element which was first repaired and then changed for another custom made one.

orphanespresso wrote:Cavitation knock is caused by flash boiling at the element ...

I stand corrected then.
Thanks Doug. =-)
It's nice to hear from you, always learn something new.

Cheers,

CIV

Thank you for the explanation Doug

My Dad and I checked for shorts even though I haven't be able to reproduce the noise and the wiring and element are fine, so the cavitation knocking seems to be the what it was.