JRising wrote:For what it's worth, the piston o-rings are QuickMill Part # OR4137. I would start with: clean the heck out of the brew unit, lubricate the new o-rings and replace the old ones.

https://www.chriscoffee.com/search?type ... t&q=OR4137

You are reading my mind! Just ordered two of those last night as I prepare to tackle this project.

It sure needs a cleaning. Couldn't pop the top piston lose from the brew unit even after manually reversing the motor. I think I'm gonna have to really soak and scrub to pop it loose.

More over the weekend!

Thanks so much for the advice!

I'm just guessing but if the machine wasn't well maintained the o rings in the piston could have hardened and fused to the cylinder wall. Finding a way to leverage onto the piston shaft and hammering the lever bar could break the seal. Hopefully nothing else. If you can spin it you should be able to pull it out.

Your guess was absolutely right! Boy were they fused to the interior wall of that brew unit. But I used your tip and, using a flat-head screwdriver and a hammer, broke the seal and got both pistons out. Thank you!

My guess is that the machine died mid brew and the guy just set the machine aside... for quite a while. All those pieces (and coffee) became one. Hahaha

Really glad to hear you got it loose. It's so good to take a machine that's been side lined by lack of maintenance and bring it back to life.

Thanks so much! I will say it felt pretty darn great to pop those pistons loose. Feels like I'm on my way to getting this poor old fella back in good working order. All thanks to you and the other folks here who have been kind enough to provide links, tips and information!

I'm only part-way there, but I'd be totally lost if not for you folks. Really grateful!

Well, thanks to the help I've received here, I've successfully taken everything apart and cleaned it thoroughly, unjammed the pistons, replaced the o-rings, greased it all up, and everything powers on and seems to slide in and out of the brew group without issue.

After about 20-30 seconds starting up, everything stops running and the "Group Error" displays on the screen again.

I'm at a loss. Does anyone have any idea what exactly the Group Error refers to? Can't find anything specific via Google.

The only local repair shop that works on the Monza has a very long wait time and charges a large hourly fee. Trying to avoid it if possible. But maybe I'm at the breaking point here.