Bezzera Strega piston seal replacement

Equipment doesn't work? Troubleshooting? If you're handy, members can help.
Jolly
Posts: 7
Joined: 12 years ago

#1: Post by Jolly »

After 3 years of good operation, the machine finally needed some maintenance. I had done a vacuum breaker replacement in the mean time, and a (one time) lube job for the piston, but that was it.

The lever started to make little jumps when moving upward, and sometimes there was water coming from above the piston (when pulling the lever down): time for the only maintenance left; replacing the seals.

I ordered 3 rings as detailed in the technical manual as part no. 7491001, and a new undercup gasket. The puzzle now, was how to disassemble/assemble the whole thing? The two little holes on the bottom of the piston initially made me wonder if complete disassembly was required. The answer was simple - do not disassemble. I took a screwdriver and gently tried to squeeze the rings over the metal edge of the piston. There it immediately snapped, the rings were really end of life and dried out. In the photo you can see the cracking of ring, on the edge of lip.


The new rings are elastic enough to get it over the piston edges. Just take good note of the placement of the rings before removing them. Top and bottom ring are there to seal downwards (main operation), and the middle ring is to seal upwards. Lubing the rings only on the outside (although arguably lubing the inside of the ring will make the placement of the rings easier), and some lube on the inside of the group cylinder. Letting the piston sit inside the group cylinder while heating it for 30 minutes to allow the lube to get to a more liquid state. Then moving the piston gently up and down a couple of times, also make sure to rotate the lever to get an even distribution on all sides.

To me it makes the Strega a real pleasure machine. Almost no daily maintenance (as in back-flushes), and a relative simple major-maintenance of replacing the rubbers, makes this machine very cheap in daily operation. And above all, very good espresso that is very hard to do wrong.

A special thanks to Kafko for the maintenance guidance.

espressotime
Posts: 1751
Joined: 14 years ago

#2: Post by espressotime »

The fact that they were dried out probably was caused by lack of maintenance.A regular lube job will guarantee a smooth lever operation and longer lifespan of your seals.
I used the same seals for little over two years and when I sold my Strega the seals were as new.

Jolly (original poster)
Posts: 7
Joined: 12 years ago

#3: Post by Jolly (original poster) »

Never thought of that, could be. Yet again, I've never noticed a requirement for it. To my knowledge it has always been sufficient lubricated. I give it a try, and increase the cleanup/re-lubrication job to a 6 month schedule. Let's how we go from there.

IMAWriter
Posts: 3472
Joined: 19 years ago

#4: Post by IMAWriter »

I check my piston every 4 months. Luckily, the inside is pristine, clean no grundge. Still, I wipe away any old Dow 111 left, and liughtly lube the outside of the seals, a wee bit in between, and VERY lightly inside the group.

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another_jim
Team HB
Posts: 13872
Joined: 19 years ago

#5: Post by another_jim »

[quote="Jolly"I ordered 3 rings as detailed in the technical manual as part no. 7491001, and a new undercup gasket. The puzzle now, was how to disassemble/assemble the whole thing? ... The new rings are elastic enough to get it over the piston edges. Just take good note of the placement of the rings before removing them. Top and bottom ring are there to seal downwards (main operation), and the middle ring is to seal upwards.[/quote]

Thanks for posting the how to, it'll be much appreciated when it comes time to change mine.
Jim Schulman

erik82
Posts: 2146
Joined: 12 years ago

#6: Post by erik82 »

Every (other) month I lube the group from underneath. When the Strega is cold just pull out the showerscreen and pull the lever down. Wipe away the old DOW-111 from underneath the group and replace with some new DOW-111. This will take you 3 minutes to do. Warm up the Strega and pull the lever a couple of times to lube it more thoroughly.

I take the shower screen out every other week to clean it and wipe away excessive greese that can be seen at the bottom of the piston. Most of the time it's just a very small amount. You can combine this with doing the quick lube job every other time.

Every 9-12 months I pull out the complete piston and clean/lube the whole thing. It's better to take the top plate of and disassemble the wires of the pump so you can pull the piston out completely. Last time it took me 15-20 minutes to do this after doing it 3-4 times prior.

This works pefectly and keeps the seals in a good shape. I took off the seals once to do a more torough cleaningc of the piston but taking them off will likely damage them because they're so tight on there. I eventually took the piston out one month after that cleaning and replaced the seals because they where damaged.

Jolly (original poster)
Posts: 7
Joined: 12 years ago

#7: Post by Jolly (original poster) »

erik82 wrote:I take the shower screen out every other week to clean it and wipe away excessive greese that can be seen at the bottom of the piston. Most of the time it's just a very small amount. You can combine this with doing the quick lube job every other time.
How do you get the shower screen out conveniently? The standard shower screen doesn't have ridges to put something behind (like a screwdriver) to apply force. The only way i could remove the screen, is by removing the lever/piston, and then push it out downward through the group body itself.

It surely sounds like more frequent lubing will benefit the Strega.

erik82
Posts: 2146
Joined: 12 years ago

#8: Post by erik82 »

Just a carefull wiggle with a flat screwdriver against the side of the shower screen. First one side and then another and back and forth. I've never had problems with the stock shower screen and taking it out. With the black gasket it's far easier doing this while the machine is hot and thus the gasket softer.

You just have to let it cool down to lube. If you don't do this water will be pushed out of the thermosyphon when you pull the lever down and without a shower screen this gives a big hot mess.

Jani73
Posts: 14
Joined: 9 years ago

#9: Post by Jani73 »

Table knife or dinner knife, whatever is the proper term, works like a charm. It goes between frame and that spot welded ring. Mine comes easily out with cold machine.

IMAWriter
Posts: 3472
Joined: 19 years ago

#10: Post by IMAWriter »

I use a paint can opener, free at the Depot or Lowes.
Juist be gentle. Still, by the time you have a few small dents in the screen, it's time to replace anyway.
Speaking of which..... :idea:

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