O-ring (id: 3.​85mm T: 2mm) 5313217701

Remove sides, back, top and front control panel following video on eReplacementparts.com web site. Remove clips where tubes connect to generator and other interior machine parts, remove tube, remove old o-ring, replace with new o-ring, replace clips. Reassemble.

remove the casing from the top, disconnect the hose with the water leak and replace the o-rings

1. Removed water tank & used coffee catcher and tray.
2. Removed sides, back, and top panel.
3. Carefully make relief in wires, and water tubes
4. Remove 4 mounting screws and the generator assembly
5. Remove water connection to generator.
6. Remove and replace connector tail piece.
7. Reverse steps 5 through 1 in reverse order.

I've had this machine for almost 10 years. 3 years ago it developed a leak. I looked at repairing it but the parts were not available at the time. We bought a new Delonghi (the 3300) and I kept the 5400 for parts as it looked like all the internal mechanical components were the same. We now purchased a cabin in the woods and wanted good coffee. These machines are pretty pricey these days so I decided to take a stab at repair again. Thanks to e-replacementparts I was able to get the parts I needed for a reasonable price. To get at the generator, first unplug the unit, then you need to remove all the outer housing panels (this should be obvious). Then the generator has 4 long machine screws holding it in place as well as 6 wires that need to be disconnected. Two are power, two are sensors and 2 are for a microswitch. I just followed the leads back to where they connected and took photos of where they plugged into so I could plug in the new generator. After unplugging the wires you'll need to remove the 4 long screws. A Phillips screwdriver and some needle nose players for the small nuts on the bottom. A couple of these nuts are hard to reach and you will need patience upon reassembly and nimble fingers. Once the screws are removed, there are two water connections to remove. they are held on by small metal clips. just pull the clip out with your pliers and the water line will come out. then remove the generator slowly. You will note a black rubber water (drain) connector on the underside of the unit opposite the side water connector. You will want to attach that one first upon putting in the new generator. Reassembly is as they say the opposite of removal. Some tips. Replace the o-rings on the two water lines (order them at the same time) or they will leak as I learned. Attach the black rubber drain line and the side water line before screwing the generator down. Once set in place put all the screws in loosely to get it lined up as it is a tight and precise fit. Get all of the screws tightened down - this is important as the generator is part of the coffee "press" and will be pushed up on when making coffee. After reassembly carefully put the water tank in (without the side panels on and start the machine and make a coffee or two. Use a flashlight to check for leaks around the generator. Be careful not to touch anything as the generator gets very very hot (it may smell a little hot at first use) and there are exposed electrical wires that pose a shock hazard. Once you confirm you have no leaks unplug again and put on the top and side panels. You are now good to go. Use this time to clean the unit thoroughly and lubricate the press o-rings with food grade lubricant. Good luck!

Remove screws on the back of the espresso machine
Remove the rear cover panel
Slide the side cover panels to remove
Remove screws and the top cover
Remove the tube ends and replace each washer, refer to the part drawing from the website
Put the top over back and test for any leaking
Put the side and then rear panels back

Done

Removed tube retaining clips with pliers, carefully used a hook and pick tool to remove ORing from inside connection to boiler. Lubricated new ORing with small amount of Vaseline to slide deep into connection to boiler. Replaced tube and retaining clips.

1. Brushed all tubing with water and soap to remove algae;
2. Descaled boiler;
3. Replaced boiler inlet tube and o-rings (suggest to use a tiny pint of Vaseline to adjust the o-ring of the boiler easier);
4. Replaced boiler valve set (this needs to disassemble it and a new o-ring is needed after);
5. Installed 2 missing rubber feet;
6. Cleaned coffee maker's base plate with sponge and soap;
7. Finally closed everything and finished work.
=> Awesome result - machine's new again!

I unplugged the machine and removed the water tank and water tank cover. Then, I unscrewed the two screws on top of the machine holding the main covers in place, and carefully pried the steam knob off. After that, taking the cover off the unit is a little tricky. There's a tab in the back that locks it into place and takes some finesse to not break while trying to take the cover off.

Once it's off however, I located the tube running from the water pump to the heating element, removed the alligator clip holding it in place, and carefully pulled the tube free from the connector. I had to fish the o ring out from the connector with a toothpick, but it was relatively easy. I then slipped the new o ring over the tube, re-inserted the tube very firmly into the connector, locked it in place with the alligator clip, and tested the machine for leaks. Once confident that the leaks were solved, I replaced the cover, steam knob, etc and screwed everything back into place.

Overall a very simple repair, just take your time and make sure to use common sense.

Opened machine
Took retaining clips off the hose
Applied silicone grease on the washer and replaced hose with new washers.
Very easy job.

Identified section leaking
Tried several combinations of gaskets and O rings and finally stopped the leak