Conti Prestina Espresso Machine Restoration 101 (Completed and Indexed)

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#1: Post by drgary »

The Completed Restoration

Update and index, February 19, 2013.

I have now completed this 22 month restoration to the point it's sitting on my kitchen counter and I'm getting to know it as my daily espresso machine. As promised here is an index linking readers to the subject matter contained. As a "newbie" restorer I've thought through all of the steps with the help of more experienced guides. Others starting a serious frame-off restoration for the first time may learn as much from my many wrong turns as when I finally got it right. In that sense this is also an "Espresso Machine Restoration 101" thread. Here then are links to the content so you won't get lost in yet another monster thread.


- Bolt removal begins
- Assessing stuck water inlet pipe
- Removing sightglass and stuck bolts addressed in earnest
- Doug Garrott on removing stuck parts
- Considering paint versus powder coating
- Stuck group studs with Ray Johns advice on removal
- Trying propane torch for stud removal after oxy acetylene torch was suggested but not available
- Assessing threading of stuck boiler bolt, Eric Svendson advises
- Mapp torch and bolt freeze obtained
- Snapping bolts with too much wrench
- Water soaking stuck boiler gasket plus mild descaling
- Trying to pry open boiler
- Assessing finishing or polishing of stainless steel panels
- JayCan separates boiler halves with oxy acetylene welding torch and cutting wheel
- Removal of stuck bolts with torch and pliers
- Drilling out bolts and tapping new threads
- Considering PID versus Sirai PSTAT
- Ray Johns advice on PID
- Intensive small parts teardown, clean-up, descaling and citric acid bath for boiler
- Oxalic or muriatic acid bath discussion, went with muriatic

Reworking parts begins

- Attempted polishing of stainless steel panels begins
- Rotary buffer tried and leaves shadowing
- Jeweling considered
- Brushed finish chosen
- Boiler clean-up with sanding and wire brushing, which destroys old drill
- Attempted cutting of boiler gasket
- Gasket cutting fails, mapping of reassembly begins
- Selecting new hardware (bolts, nuts, washers) and preventing rust
- Finishing boiler to seal with gasket


- Reassembly begins!
- Addressing heating element terminals
- Rebuilding steam and water taps
- Specifying materials, choosing and fabricating plumbing and heating element gaskets and o-rings
- Punching viton gaskets
- Taking apart piston assembly and creating a large spring clamp (first try)
- No clamp needed to unscrew piston from spring
- Remounting on frame
- Sizing plumbing starts
- Group rebuild
- A better spring clamp, attaching water fill pipe, torquing boiler bolts
- Rebuilding manual water inlet valve
- Reworking a stripped fitting and attaching manometer
- Assessing vacuum breaker and replacement PSTAT
- Starting design of drip grate
- Puzzling over pipe fitting and plumbing
- Choosing perforated metal drip grate design
- Sightglass rebuild
- Synesso drip grate chosen as workpiece
- Pipe fitting struggles
- Pipe sweating supplies and drip grate parts procurement
- Ray Johns advice on sweating pipe
- Rewiring starts, beginning with PSTAT
- Sirai PSTAT placement per Eric Svendson
- Figuring out circuit diagram
- Crimping wires without solder (first attempt)
- Soldering wire connections

Testing and finishing

- First shot on Christmas Day!
- Pressure testing and fixing valve leaks
- Choosing thread locker or sealant
- Drip grate fabrication starts, using jigsaw on stainless steel
- Drip grate extension designed
- Considering a fuse or thermal protection
- Soldering wires
- Reassembling the case
- Testing stock Sopac PSTAT reveals wide deadband
- Testing temperature profile of a pull with a data logger and Artisan software
- Struggling to install Sirai PSTAT and vacuum breaker without leaks
- Cutting stainless steel drip grate extender using jigsaw
- Securing PSTAT, Taps and Wires
- Start-up unattended with water tap open causes water short and trips GFCI
- Routing vacuum breaker drain to drip tray
- Puzzling over thermal safety devices
- Sealing electrical contacts with Rescue Tape, installing push to fit connection, insulating boiler
- Filing drip grate extender to fit
- Installing machine in my kitchen
- Precision fitting, gluing with JB Weld and clamping drip grate
- Attaching edging rails to drip grate
- Tricky fitting and clamping of drip grate rails
- Done!
- Restoration notes

- Addendum: Post-Install Servicing and Leak Prevention

This is where it all started: :roll:

Hello All:

I'm starting to rescue my Conti Prestina and share a few photos of the teardown now underway. This will take some time as available on weekends -- the boxes in the background show that I'm stealing some time from an ongoing move-in to our new home.

(Later add: Since I'm new to a total teardown and restoration, I want to document this carefully so it can be a primer for others new to that process. It might also help with such details as how to make a gasket, how to deal with stuck bolts, etc.)

Much appreciation to Doug Garrott, Lucio Del Piccolo and Ray Johns who've already contributed suggestions. See Doug's video tours of the Prestina under the hood and of plumbing her in for bottle feeding via Flojet So I now own a working, used Flojet.

For those wanting to view more pix and in more detail, here's a link to my Picasa album so you can zoom in to high res imagery of rust, gunk and great espresso machine design:

Here's the plan:
1. Preparation included getting most parts and gaskets. Now there are matching knobs, portafilter, etc. Per Doug's suggestion I applied a multitester to the plug and get a nice, steady signal with some low resistance, so the heating element works without shorts. The worn plug and probably power cord will be replaced.
2. Teardown, putting parts in labeled and inventoried bags with large parts in boxes, noting and photographing what I find each step of the way. Teardown will of course include removing wiring, removing old gaskets.
3. Send out for professional chrome plating and powder coating. This will be done along with parts for my Olympia Express Coffex, which I'll soon also tear down and rebuild.
4. Thoroughly clean and descale parts
5. Order any needed replacement parts, including fabricating drip tray and grate if these cannot be obtained.
6. Reassemble and test
7. Nothing but crema!

Later add: 1/30/12. I found this excellent repair schedule on an old web site by Paul Pratt. Will mention it later in the thread too.

The Teardown

Let the fun begin! Here are a few pix of the teardown:

Knobs Removed

Cup tray and rim and top of group case removed:

Fully disrobed, side view:

Nekkid, grungy and showing off, front view:

Wiring close-up. To the right, a leaking sight glass seal is shown by rust underneath it. Sight glass is also heavily scaled:

PStat seen from bottom:

Grouphead close-up:

Piston and spring assembly removed with lever in cocked position (Doug, with your permission I'll post your instructions on how to do this):

Guide tube removed, looking into the gritty state of the piston cylinder and filthy shower screen:

And then the first sticking point! One of four bolts that secure the bottom of the group came out easily. The rest won't move after one minute heating with a propane torch. I've read elsewhere that adding penetrating oil won't help because it burns away. Is that wrong? Should I get an impact screwdriver with metric hex bits for this?


What I WOULD do for a good cup of coffee!

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#2: Post by orphanespresso »

What a sweet little project you have there! That you are taking a casual approach and not pushing too hard seems good as well...
First, someone got real creative with the electrical system and the under slung pstat is a touch...the wiring looks pretty hazardous. I like the big strain relief knot in the cord. Glad you took my advice and pulled the lever down before taking it can see that you can do a lot of cleaning and then release the lever and do the rest. As rusty as it is it looks like removing all the linkages and clean then grease will be in order. No rust on the spring though!

I would take it nice and slow on those stuck bolts...Kroil or other penetrating oil wherever you can get it in, and since you can put it on a wait a week, it might help. Once you have soaked it take a hex socket, not a key but a hex mounted in a socket and put it in the cap bolt head nice and firm and give the top of the socket a real good strike with a hammer to try to shock it loose. Put the handle on the socket and try to tap it tight then loose...just tap tap tap back and forth to see if you can get even a little movement. If you can get it to move at all add more oil on the threads and keep at it back and forth. If this does not do it then a Detroit Wrench will be in order (oxy/acetylene). Likely not enough heat in propane with all that metal. It might be best to remove the group from the boiler before you do the steamfitter's blow on the bolts.

By the time you are done with this you will probably have a nice little workbench repair shop going for yourself in your new garage!

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#3: Post by drgary (original poster) »

Thanks, Doug. You must have that sleep thing I do that comes with middle (hah!) age ... just pushed past 60. First to the stuck bolts. Great advice. I'll give it a try. If it fails, Lucio suggests there are some things that just don't need to be disturbed if they won't budge. Can I clean that thing adequately if I can't get those bolts off? Other questions for you or others:

1. I was looking at that crude Pstat and wiring and wondered whether it might be good to upgrade that. Also am thinking about whether to insert some sort of temperature read-out in the process along with pilot light and heating element light. A round temperature gauge would fit in the hole that's already drilled in the front of the case and was covered by a chromed cap.

2. Is there a gasket missing on the piston?

I look at this project as a way to learn many things about restoration. It's a classroom for me of sorts. :D

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#4: Post by kitt »

I'd definitely upgrade the pressurestat wiring, hard to tell from the pics but the existing wiring looks to be quite thin for 110V.I used a new Mater on my Empress because i've never had a problem with them here at 240V.You may be better off going with a sirai at 110V, but that may involve a new pipe and mount for the pressurestat.
Good idea on the lights, i'm not convinced on the merits of a temp gauge on a lever machine, as the grouphead acts as a big heatsink, affecting the brew temp alot.
The piston looks to have 3 seals, which is normal.The gap is usually at the water inlet level, to allow water to ciculate around the piston (hence the scale on that part of the piston)

Good luck with the resto, looks like lots of fun.The first few are usually a big learning experience with lots of "oops, i'll do that differently next time" moments :)

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#5: Post by drgary (original poster) »

kitt wrote:... i'm not convinced on the merits of a temp gauge on a lever machine, as the grouphead acts as a big heatsink, affecting the brew temp alot.
Thanks for the great suggestions, Mike. About the quote above, as I'm learning this lots at a time, of course. If I set the Pstat correctly, that will control my temperature enough that I don't need to worry about an actual temperature gauge?

I'll look into the Sirai pressurestat and will definitely replace wiring. Both you and Doug agree the wiring looks way sub par. A new pipe and mount shouldn't be too hard to do, especially since Doug shows an example in his video tour of a restored Prestina. I could simply do it that way.

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#6: Post by kitt »

drgary wrote:Thanks for the great suggestions, Mike. About the quote above, as I'm learning this lots at a time, of course. If I set the Pstat correctly, that will control my temperature enough that I don't need to worry about an actual temperature gauge?
The pressurestat setting does affect the boiler pressure, which in turn has a small affect on brew temp, but the biggest factor is the grouphead idle temp, and flush routine.most commercial levers, once up to temp will need a small warm up or cooling flush before brewing.They're all different depending on the boiler design/grouphead design etc, but you'll soon get a feel for what works with your machine.There's alot of design/thermal dynamics at work in these groups, and they just seem to work.I've rarely had a bad shot from a commercial lever, and when i have, it was usually grinder related.

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#7: Post by Warrior372 »

You guy's like that wiring job to eh? My '91 Prestina came the same wiring job. . . That must be a stock factory wiring job. I did not have the retention knot though.

Several of the bolts on my Prestina were firmly rusted into place and no amount of penetrating oil would do the job. I applied it several different brands multiple times a day and a few just did not want to budge. I eventually found that using an incredibly tight pair of locking vice pliers worked much better than a wrench on the stuck ones. After gripping them with the vice pliers I would then hit the pliers with a rubber mallet. I did this for a week or so, got a few out and then moved on to a more aggressive method. I ended up getting the other bolts off using 2 cans of bolt freeze from my local automotive supply warehouse. It gets the rust too such a low temperature that it creates pores in it, allowing you to apply more oil and hopefully remove them. I could not remove one of the bolts, so I just ended up drilling it out and rethreading the hole.

In regard to the piston. No, you are not missing a gasket. I asked Scott, the head tech at Allann Bros, the same question when I was rebuilding mine and he said that they were designed this way and that every one he had ever worked on had this setup. I believe he stated a reason for it at the time, but I cannot recall the specifics.

Mine actually came with a Sirai. The individuals I purchased my machine from were the original owners and had never replaced anything on it. Heck with the condition it was in when I got it I would be shocked if they had ever used it. It looked like it was sitting on (not in) a barn for 10 years. The Sirai was shockingly clean as compared to everything else on the inside and outside of the machine. With that said, it is a '91, so Conti may have switched parts somewhere along the line.

I do know Cara was actually an espresso machine distributor out of San Francisco. I noticed the company name on he front of your machine. They purchased and rebadged machines from Conti. The '52 2-group Empress I have is a La Cara. Shortly after purchasing it I sought out 'La Cara' to get more details on my machine. I ended up getting in touch with the son on his personal cell phone, he was quite shocked that I had tracked him down. He said that his father had started the company and they no longer carried Conti's. He did not have any detailed sales records to refer back to either.

How did the parts search go? Were you able to source all original parts? If so, I would encourage you to keep the machine in it's original condition and forgo the fancy modifications. There are so few Prestinas floating around it would be a shame to mod it from it's original design. With that said it is your machine, so if you are going to mod it then go big with it. It is like modifying a Ferrari. If you are going to do it you have to go real big! :)

P.S. - Great video on the Prestina Doug & Barb! I remember the tight setup of the front face plate too well. It made it quite fun to disassemble / reassemble. I really enjoyed the overview of the group. Nice Job! I tried leaving the comment on youtube, but it would not post for some reason

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#8: Post by drgary (original poster) »

Hi Michael:

Thanks for joining us. First some good news. The hex bolts came right off when I applied a socket hex key with a little finesse and without so much as a light hammer tap or penetrating oil. Thanks, Doug, for the suggestion! Here's a photo:

La Cara was the company name for Thomas E. Cara, Ltd. and Thomas, Christopher Cara's dad, was quite a pioneer in importing these machines. The original shop is still open and sells La Pavonis and one of the Vibiemme Domobar models. He may also sell other home levers but I would have to check. I started a thread about Christopher elsewhere on this site Any Questions to Ask Chris Cara? and wrote up a lesson from him A Lesson from Christopher Cara in Using a La Pavoni Home Lever Espresso Machine.

About modding the machine, Michael, so far I can't find all the original parts, specifically the drip tray and grate and the front Conti name plate. One of the other name plates on the machine is dinged, also, and I just crinkled the serial number plate taking it off the front panel so I can have that piece chromed. I don't think these are worth a lot as collectibles compared to some of the older, more classic commercial levers. (Doug and others, correct me if I'm wrong.) There's been some discussion here about the relatively low value of vintage espresso machines at least so far. Dan (HB) recently commented in a thread Is there a "Blue Book" of used espresso machine values?, and here's a brief discussion I started: How to Evaluate Collectible Espresso Machines? I became curious about that topic when I stumbled upon a rare Lady Duchessa that I've just gotten back from Doug, beautifully and faithfully restored. Compared to your Conti Empress, a Lady Duchessa, a Faema Lambro or this amazing Faema Marte, see: Lever Espresso Machine Gallery, I think of the Prestina as kind of an ugly duckling that's brilliantly designed to pull shots and take up little counter space. FWIW the mods I'll do aren't irreversible. I've already been talked out of installing a temperature gauge, but that drip tray looks like it may need to be fabricated, and it may be more of a pain than it's worth to try and duplicate factory spec, which doesn't appear to be the epitome of Italian design.

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#9: Post by Warrior372 »

Orphanespresso just sold a Conti Prestina for $2,400. So yes, you could say a Faema Lambro is worth more, but in regard to machines I have seen sold on that site in the last 3 years that is a pretty high number. I think someone who collects anything has to value an all original piece higher than a modded one (That is just my opinion, and I am sure others have their's too). That number is very close to what I got my Prestina estimated at by a european collector / rebuilder several years ago, he actually said $2,500. He said the machine was considered to be so unattractive when they first came out that very few people in Europe and even fewer in the US ever purchased one, making it one of the rarest lever machines. Because of that he said they are much more valuable to collectors, which makes sense.

How do your boiler nuts look? Those are the ones I had the real trouble getting off. I agree that the stock drip trays are not the flashiest . . . but neither is a '57 chevy factory hub cap in my opinion :) .

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#10: Post by drgary (original poster) »

That's really interesting, Michael. I didn't know I had something so valuable!

If I could find an original drip tray that would be great. In any case I will put it back into top shape and if an original drip tray is found, so much the better. What I will have made if that must be done will look very professional.

To see the bolts I removed closer up, here's the Picasa link for an image you can magnify ... directlink. There are other pix in the Picasa album (see link above) that show the boiler bolts. They look ok. We'll see. I won't be able to get to that right away, and if the boiler doesn't leak, I may not open them because I'll have to fabricate a boiler gasket from scratch.

What I WOULD do for a good cup of coffee!