# Gaggia Classic pulsing when brewing



## Wired (Dec 9, 2010)

My much beloved Gaggia Classic has recently started to pulse when brewing shot.

It seems to occur when the coffee is tamped to the required pressure and you expect a decent shot.

If I loosely tamp the grind the pulsing doesn't occur but the resulting shot would brew to quickly.

Its almost like the pump is struggling to pump the water at the required pressure through the grind.

In the past when I've ground the coffee to fine, the brew would just drip but there would be no pulsing from the pump.

Is the pump on the way out or is there any other explanation?

TIA.


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## Charliej (Feb 25, 2012)

When did you last descale the machine? or backflush it there could be scale and all sorts of crud in the pipework of it , if you can give us an answer to this we can then advise further if necessary.


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## Wired (Dec 9, 2010)

I des ales and back flushed about a week ago and I've noticed the pulsing since. I use filtered water and generally descale every month (few months sometimes).

I've had the Classic for approx 5-years and have only ever replaced the group seal and steam wand due to leakage.

Thanks.


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## Charliej (Feb 25, 2012)

It could possibly be a small piece of scale jammed in the solenoid, causing the solenoid to not be able to open or shut properly. I think there is a guide to locating and stripping one somewhere on the forum if you check the "So you've just bought your Gaggia Classic "sticky in this forum it could be in there.


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## Wired (Dec 9, 2010)

Thanks for the reply. Does my Classic's symptoms sound like a pump which is on its last legs?

Why does the water flow normally with a slightly coarser grind?

I'll try stripping the solenoid.


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## El carajillo (Mar 16, 2013)

If you type in gaggia solenoid in the search box top right it will take you to a page where I placed a short note on removing the sol/valve ,dated 13-05-13. The ports in the valve are very small so could quite easily be a flake from descaling.


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## Wired (Dec 9, 2010)

Well I finally had time during the weekend to remove the solenoid. Considering its 6-year old machine, the solenoid looked like it was brand new! I blew through both ports and couldn't notice any blockages. Could there still have been scale in the different ports?

During the removal I noticed that one of the allen screws securing it to the boiler was loose. After re-attaching it to the boiler I made sure that both allen screws were firmly tightened. I had high hopes for my first brew but alas no change, still the pulsing occurred. Its like it hasn't got the guts to force the water through the grind at the required pressure.

Before the second brew I thought I'd back flush with just water as I'd only recently back flushed with Califiza. One thing I noticed was there wasn't the normal whoosh you get when the water gets sent to the drip tray. It got slightly better after a few cycles but still not the pressure I remember when I've back flushed in the past where the pressure would be so great when the water gets sent to the drip tray, the Calfiza solution would foam up.

I noticed there was some scale bits in the drip tray, so maybe I dislodged something?

I have to say, the second brew was better in terms of the pulsing. Flow was better although there was still pulsing.

Any other suggestions?


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## painty (Jul 25, 2011)

It does all sound consistent with the pump becoming weak as you suggest. They sometimes pop up on ebay at good prices

BTW have you checked for water returning to the tank via the over-pressure valve? I guess a weak OPV could be another possibility.


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## Wired (Dec 9, 2010)

Painty how would I check for the water returning via the OPV? Do you know how much a new pump would cost if I bought from Phillips and are they easy to replace?


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## painty (Jul 25, 2011)

Classic has two tubes going to the water tank - one to feed water to the pump, the other to return water from the OPV. There's a procedure for checking the OPV setting by referring to the Ulka pump's flow vs. pressure graph where you just measure the amount of water returned via the OPV tube in a given time (not as difficult as I make it sound) perhaps one of the Classic owners can give you pointers or links on this.

Less formally, if you were seeing water returned to the tank during a coarse-ground, too fast, shot, that would indicate it is opening at too low a pressure


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## painty (Jul 25, 2011)

Without having checked closely, this might be the one

http://www.ebay.co.uk/itm/400403243365

I'd suggest checking against the part number fitted on your machine before buying. They are pretty easy to replace if you are happy using basic tools.

Worth bottoming out the OPV possibility before buying though


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## Wired (Dec 9, 2010)

Oh that's the pump. I'm sure it can't be too difficult to replace. I'd be interested in hearing how to rule out the OPV from someone who would know.


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## painty (Jul 25, 2011)

Wired, since no one has come back to you on this, I've got a few links that will give you the procedure for checking and if necessary, adjusting the OPV. Maybe one of the Gaggia experts here can help out further:

Ulka performance graphs http://www.ulka.it/admin/moduli/m003_web/file/pag_ULKA_web.pdf

http://www.jamesgleave.com/2012/07/96/modifying-gaggia-classic-opv-to-9-bar/

http://www.toomuchcoffee.com/index.php?name=PNphpBB2&file=viewtopic&t=2479

http://coffeesnobs.com.au/brewing-equipment-midrange-500-1500/25325-gaggia-classic-pressure-modification.html

Hope that is some help


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## zdgrunf (May 15, 2012)

Your problem is preasure, check the opv and adjust it. I got same problem with wrong preasure.

Sent from my LT22i using Tapatalk 2


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## Wired (Dec 9, 2010)

@painty

Thanks for those links. Some interesting stuff there for me to digest.

Interestingly enough, on Sunday I had a compulsion to do some back flushing. A few cycles with Calfiza and a few with water from group head. The result was some scale deposits in the drip tray.

Made my morning cappuccino on Monday and no pulsing! Made one again this morning and still no pulsing. Did one water back flush cycle today as well and found tiny bit of scale.

The lack of 'whoosh' I described earlier in the thread when back flushing seems to have gone but still not the level of whoosh I've had in the past.

Any more ideas?

Thanks to everyone who's contributed so far.


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## Wired (Dec 9, 2010)

*** Double post ***


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## haz_pro (Apr 4, 2013)

If scale is still coming out then maybe do some more back flushing and descaling.


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## PaulN (Mar 10, 2011)

An important part no one has asked is hows are the shots?

Id have said your OPV might need adjusting, but ive set mine to 9bar and without trying and listerning it does labour a little more when pulling a shot with very fine grind.

The origianl 15 bar for me was way too high.


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## El carajillo (Mar 16, 2013)

There is an video on the I/net at the BEZZERA factory explaining pump pressure on commercial and domestic machines.It shows the pumps running nd explains WHY the difference in settings.Commercial pumps run instantly at 9 bar (rotary) domestic (vibe) pumps gradually ramp up to set pressure and deteriorate with age.

BEZZERA set their domestic machines to run at 11 bar and recommend adjusting to this. Very interesting video and very informative (it starts off in German but continues in English)


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## glevum (Apr 4, 2013)

I cranked my Bezzera up to 11 bar after watching this video, coffee did not taste right at all. Back at 9.5bar


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## Wired (Dec 9, 2010)

Thanks for all the replies. I should really tell you all where i'm at. I'm pulling shots with a Gaggia Classic (my trusty 7-year old friend!) and have recently moved from pods (for convenience more than anything) to HasBean espresso ground.

The pulsing seems to have gone. This may have something to do with me backflushing more regularly now along with the OPV mod. I'm waiting for the bits to make a portafilter pressure gauge to check the pressure properly. I've a suspicion the pressure is still to high.

After spending bit of time roaming this and a few other coffee forums, I've come to the conclusion that I'm currently having to overdose to get the flow at an acceptable rate, even then its not perfect.

I'm now toying with the idea of purchasing an entry level grinder to grind my own.


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## Wired (Dec 9, 2010)

Bit of an update. Put my portafilter pressure guage together today and after doing the OPV mod 3/4 anti-clockwise turn without a guage, the Classic's pressure was at 12 Bar. After some fiddling, the pressure now stands at between 9.5 - 9.75 Bar.

Using Hasbean's Brasil Perfetto expresso blend the flow is too fast. I pull doubles most of the time and I get about 50-60ml in about 15 seconds no matter how much of a Gorilla tamp I give it. Without dosing to about 20g, the flow is even faster!

Would I be right in thinking that I need a finer grind?

If thats the case (bearing in mind I don't haves grinder) does anyone have any experience of Hasbean's espresso grind and any facility to order it finer?

TIA.


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## xiuxiuejar (Jan 24, 2012)

In theory you need a finer grind but it may be the beans or the tamp. In fact, I have some dodgy Sumatra beans through which the water passes too quickly and grinding too fine will just clog up my machine. There is always a point where you should not go finer. Try tamping at half the dose and again with the whole dose just to see if it is how this particular coffee is distributed in the filter. I know it sounds silly, but some coffees don't distribute as evenly as others and you need to give them a swirl with a toothpick or ensure your tamp is super even. Other coffees are just easy. It depends on the roast and the humidity of the bean I suppose.

It's just trial and error but careful not to choke your machine or you may cause problems similar to the one you explained.


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