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Gaggia Classic - Loss of Steam Pressure

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Posted (edited)

Morning Folks,

Have recently given my ten year old Gaggia Classic a bit of a refurb.  Replaced the stock steam wand with a Rancillio and also swapped out the steam valve for a new one as it was constantly leaking.

Everything works fine during the brew but there is now an issue with the steam.  Just before the steam light comes on, there is a loud rattle from inside the machine which dies away just as the boiler gets to temperature and the light comes on.  Ok, so I ignore this and steam the milk, but there is not the pressure and volume of steam that I used to get, making the foaming of the milk harder.  

Initially, I though the noise was water leaking from the boiler from the joint with the new steam valve and rapidly boiling on the surface metal but this doesn't appear to be the case.  Without the lid on, I can see that the rattling is air and water being quickly dispensed via the expansion valve, down the clear plastic pipe back into the tank, presumably causing a drop in steam pressure.

Any ideas would be appreciated,



Edited by mirkl
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Posted (edited)
40 minutes ago, Blue_Cafe said:

Stuck OPV?

Could be - its not been serviced since I bought the machine.  With the new steam valve I guess the OPV is working harder as pressure is not being lost through the dripping wand.  May have caused it to jam.

I'll have it out tonight and report back


Edited by mirkl
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Well that didn't go well!

Took the OPV out and soaked in in citric - didn't look to crusty.  Put the OPV back in and electrocute myself on the steam thermostat (I know!).  

Anyway, machine powers on, water pumps through the group head.  Flick the steam switch and wait.  Boiler heating up but no steam light and now a slight burning smell.  Turn everything off and let it cool down.  Turn it back on, no power to pump or boiler.

I'm guessing I blew the steam thermostat when it gave me the shock.  The thermal fuse then blew because the boiler overheated as I waited for the steam. 

So I think I need a new steam thermostat and a thermal fuse and also a lesson in electrical safety.  Would you agree?


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1 hour ago, mirkl said:

now a slight burning smell. 

You should be able to track down what it was - the thermal fuse is on top of the boiler so easy to see / smell if it was that.  Good luck. 👍

As an aside ...one  of the nice things about a PID is you can see if it is at the right temp or not.  Lights can be off for a number of reasons.

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  • 3 weeks later...

Just jumping on this thread as I have exactly the same problem of dropping steam pressure, also with a new steam valve and Rancillo wand with a similar age machine. Just wondering whether you managed to solve the original problem Mirkl/Matt, not the problem involving A+E....

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DLM.  Having damaged the thermostat and fuse with my previous misadventures, I decided to completely strip the machine down for a full service, boiler and all.

On reassembly , everything was functioning as normal and I suspect that a thorough clean of the boiler and OPV may have removed any particles that were causing a loss of pressure.

I've learnt tonnes about the machine's workings by doing this which has given me the confidence to undertake just about any future repairs. Would recommend.

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