Gaggia Classic O Ring Problems

[stephen28]

Hi. Can anyone shine any light on this problem - Lately the portafilter on my Gaggia has become very difficult to insert into the grouphead. Possible reason may be that it is expanding under heat. I thought it may have been a worn O ring so I replaced it a month ago. This hasn't solved the problem.

At times I just about need a shifting spanner to get the portafilter to insert. To make things even more interesting the O ring sometimes has a mini explosion and becomes quite pliable and the opposite occurs - portafilter inserts easily. This tends to occur after frothing milk.

By next session it reverts back to its old difficult hardened self. Go figure! The machine still pours a great shot except for this problem.

Any ideas anyone?

[JojoS]

If O Ring means group head gasket, make sure your are using the correct thickness. If for some reason the gasket is slipping down when the machine heats up, you can coat the topside of the gasket with food grade silicone grease so it sticks in place.

[timmyjj21]

A few possibilities that come to mind...
Are you using the original aluminium dispersion plate, or an aftermarket brass one? The brass ones can sometimes have issues with letting the group seal slip. If you are using a brass one, let me know and I'll discuss further. This issue should never occur with the original aluminium one.

Is the group seal inserted the correct way around? Rounded edge goes in, with the right angle edge on the outside to create the seal on the portafilter. If it is in the wrong way you can have a difficult portafilter fit and pressure leakage as described. I always recommend the 8.5mm blue Cafelat silicone group seals, as they are so much nicer than the filthy black rubber.

Are you over filling the basket? The standard double Gaggia baskets can't really handle much more than about 17g, and by 18g you are usually compacting the grinds on to the shower screen and make thenportafilter difficult to fit. This is depending on the type and roast of the beans so weights can of course vary, but it is worth double checking.

The portafilter should never have mini explosions. The solenoid valve is there to prevent it, and when not pouring there is a direct line through the solenoid from the portafilter to the vent pipe, so it should not be physically possible... that said, I have had inexplicable issues like this in the past that took a bit of nutting out to fix!

[stephen28]

If O Ring means group head gasket, make sure your are using the correct thickness. If for some reason the gasket is slipping down when the machine heats up, you can coat the topside of the gasket with food grade silicone grease so it sticks in place.

Yes the head gasket. I haven't tried this. Thanks for the tip.

[stephen28]

A few possibilities that come to mind...
Are you using the original aluminium dispersion plate, or an aftermarket brass one? The brass ones can sometimes have issues with letting the group seal slip. If you are using a brass one, let me know and I'll discuss further. This issue should never occur with the original aluminium one.

Is the group seal inserted the correct way around? Rounded edge goes in, with the right angle edge on the outside to create the seal on the portafilter. If it is in the wrong way you can have a difficult portafilter fit and pressure leakage as described. I always recommend the 8.5mm blue Cafelat silicone group seals, as they are so much nicer than the filthy black rubber.

Are you over filling the basket? The standard double Gaggia baskets can't really handle much more than about 17g, and by 18g you are usually compacting the grinds on to the shower screen and make thenportafilter difficult to fit. This is depending on the type and roast of the beans so weights can of course vary, but it is worth double checking.

The portafilter should never have mini explosions. The solenoid valve is there to prevent it, and when not pouring there is a direct line through the solenoid from the portafilter to the vent pipe, so it should not be physically possible... that said, I have had inexplicable issues like this in the past that took a bit of nutting out to fix!

All original fittings on the Gagg. So nothing different there. The machine is getting on a bit but only used at work for 1-2 coffees a week day approx. 40 weeks a year.

I've changed the group seal a number of times over the years and haven't encountered this before. Last group seal a black rubber job bought from Coffeeparts. I don't think I've inserted it the wrong way but you never know. Might be worth trying a silicon one.

Definitely not overfilling the basket. The portafilter is hard to get in with no coffee in it!

Solenoid was replaced about a year ago. I presume it is fine. As I said the pour and shots produced are great given the age and capacity of the machine. I have a Giotto at home and sometimes think the shot from the Gaggia is equal if not better. Just not loving the tight fit and the occasional explosion from the group head and the accompanying spray of coffee. The first time it happened I thought the machine had short circuited!

Thanks very much for your suggestions Timmy.

[JojoS]

If the portafilter is difficult to lock in even without coffee in the basket, you will need to check the alignment of the portafilter with and without the basket. Perhaps the portafilter was dropped and became slightly uneven.

[timmyjj21]

Cool, all sounds good then.
As above from JojoS, check allignment.
The black rubber group seals can be a bit subtle with the markings so its something worth checking.
Has it had a good backflush recently? Just in case there is a blockage preventing pressure venting...but realistically this wouldn't effect portafilter tightness, unless the collar is filthy with old grinds sprayed around.
I'm a little stumped... I'm in Melbourne and fairly free next week if you are central/ east and would like a second set of eyes to have a look?

[stephen28]

I don't think there's an alignment problem. I'm pretty sure the portafilter has never been dropped.

A decent backflush might be worth a try. I will do this. It is given a reasonably thorough clean each time it is used and also when replacing the seal about 2 months ago so.

I should disclose that the machine is 14 years old and has given many years of wonderful service and perhaps it is "nearing time". However I'd like to think it's not an old age issue!

Myself and another experienced snobber are also stumped. Thanks for the offer to look at it. It is located in the southern suburbs - not quite in your zone. I'm thinking next stop is starting again with replacing the seal.

[timmyjj21]

To be honest 14 years shouldn't be a problem in my experience. I just spent the past few years in the UK fixing many 'broken' ones as a hobby and they are so bomb proof you can always get them going again!

If you can, you could also find another gaggia and swap portafilters to see if it is the boiler head/group seal or a portafilter/ basket issue.

[stephen28]

Yes a bit like a favourite old aunt - "the old boiler might have seen better days but you'd still like her to stay around a bit longer". Will try your swap the portafilter suggestion.