We have a 5 year old la Vibiemme Domobar Super lever, and had it serviced in Feb '10.
We make about 30 - 35 coffees a week.
In the last month it's shown an interesting problem: after a shot the group head retains some pressure after the lever has been put in the down position. This pressure inside the filter basket means the coffee explodes out of the filter holder when I go to remove it. Note that the lever is in the down position and the pressure is supposed to be directed down the exhaust thingy behind the group head.
It's intermittent. One shot in say 10 will do it. The rest are fine, whereby the pressure is released down the back and no pressure remains in the filter holder.
Most disconcerting. I've searched here for similar posts but maybe my terminology is failing me and I don't know the terms for what is supposed to happen after each shot.
All year we've been cleaning weekly with 'Puly-Caff' - back flushing with it, and soaking the filter basket.

To top it off, the most recent symptom is that the problem I describe above occurs when backflushing with the cleaner!! It's like there's a blockage somewhere.

Does anyone here have a term for this problem? Like 'failure of x to release basket pressure'.

And can anyone suggest a fix?

Brian

quattrocchi wrote:This pressure inside the filter basket means the coffee explodes out of the filter holder when I go to remove it. Note that the lever is in the down position and the pressure is supposed to be directed down the exhaust thingy behind the group head. It's intermittent.

It's five years old, so it's possible that the lower valve stem has worn down. Disassembly is in order; see Problem with backflushing Isomac Tea ll for more details.


Please do not copy this image.

Note: Stefano came to the same conclusion in the aforementioned thread:

stefano65 wrote:The kit that I made is for normal wear and tear parts
the springs,shafts,seat are not necessary to replace UNLESS they look worn out
my guess is that your grouphead not only is completely gunk out with coffee but the 2 square spindles are not square anymore and they developed an edge
of course mine is just a guess

This other problem may be related. About a month or two after a service this year I noticed this brass bushing protruding out the side of the E61, on the spindle the lever/cam etc are on. I emailed these pics to the service agent and followed up with a phone call. They said that this action is normal, not to worry about it.

Good advice?


While brewing this brass bush is pushed out. It returns at rest, but never quite fully home.


At rest.


Brewing.


Showing the pressure. Note the cloudy gauge 'glass'. It returned from the service looking like both gauges had been wiped with acetone!

Thanks

The brass bushing action is normal.

When you lower the lever from the mid position, does it feel like you are pressing against a spring?
If yes, and always, it's unlikely the cam and piston are overly worn.

If water is always released out the bottom even when the group sneezes, it's also possible there is some crud floating around above the dispersion bolt that blocks the pressure release. Remove the screen and dispersion bolt and flush well.

Do you know what 'service' was performed?

You need to turn down your over pressure valve. If that photo of the pressure gauge is during a shot and not a blind basket flush, you are brewing at 12 bars. Way, way high. It should be around 9 bar during the shot. When the machine is off and cold, does that gauge read 0?

An excerpt from Buyers Guide to Vibiemme Domobar Super

The OPV (Over Pressure Valve) is located in rear of the machine. For those of you new to the espresso machine world, the OPV controls brew pressure by venting excess pressure from the pump and returning the water back to the water reservoir. The Vibiemme has one of the heaviest OPV's I have seen. Once the outer shell is removed, you can access the adjusting screw through an opening under the water reservoir. The angle is a bit awkward but still usable. It would be easier to access if the opening was cut a half inch lower. To adjust the OPV, turn the screw counterclockwise to lower and clockwise to increase.

As Dave stated, the brew pressure gauge is showing an excessively high pressure. Also, I just operated mine a few times and the bushing does not move as yours is shown to be doing. Your machine also looks a bit grungy, particularly the crud on the lever's shaft. I wonder if the insides of the group look the same?

The lever action first of all feels ... gritty, especially after a clean with PulyCaff.

That said, I can detect some spring pressure from mid-lever position to down-lever position.

We are frantically hunting for our copy of the service sheet...

Thanks for all the advice.

deity6667 wrote:By any chance was this service done by espresso engineers in Grey Lynn? they do have a tendency to 'tweak' the OPV to around 12 bar! and raise the pressurestat so it goes off just under 1.5

I agree with Dan i think a disassembly is in order. Just remove the two allen bolts from the lever assembly and have a look at the condition of the stems.

Yes, it was Espresso Engineers. When I questioned the 12bar they said that with the kind of pump on the VBM 12 bar = 9bar. Have you altered yours to read 9 bar?

This weekend is disassembly time.