Breville Dual Boiler Rebuild

Equipment doesn't work? Troubleshooting? If you're handy, members can help.

#1: Post by grufromtheloo »

I have already been on this for a few days before I thought "hey, maybe others are interested". I will log my steps here, as I am not sure anyone else has documented a full rebuild. This may fail. This may work. I maybe blow up in the process. We will see....


I bought a project BDB either to fix up or use for parts. To be clear I currently have a new BDB I use for my everyday machine. Figured this would be a good way to gain some experience, get some parts and maybe make a little money or at least get my money invested back.

This is my journey so far

Purchase Day

I was told the machine leaked from steam valve (known issue) and that steam boiler was offline. Figured it was maybe a re-gasket the valve and replace the thermal fuse kind of job.

I get the machine home, pull the cover off. It's a war zone. There is some form of rust or corrosion on almost every exposed metal surface. There is so much corrosion that the leads to THREE of the steam boiler sensor have rusted off. Clean off. No wonder the steam boiler is offline. The metal band holding the thermal fuse on has rusted through and the steam boiler thermal fuse is just sitting there. Two or three marettes inside the machine have melted from the heated. This is in way worse shape than I anticiapated.

Here is view of the carnage

Initial Testing

It was clear the machine was in _bad_ _bad_ shape. Knowing the steam boiler leaked, I wanted to take the steam pump offline. To get at the steam pump power connection you have to

1) remove top cover
2) remove back panel
3) remove panel over the white control box

By pulling the white control box out a little this exposed the power connections. I pulled both white and read wires off the steam pump.

I proceeded to plug in the machine and test the brew path. To my delight everything worked. It didn't even leak. I could pull about 7-8 bar at the group without issue. I checked the NTC temps in the diagnostic menus and the brew boiler, group head looked good. Steam was at room temp. As expected.

Steam Boiler Inspection

Give the brew group work I wanted to know just how bad the steam boiler was so I removed the water sensors and they looked like this

It is clear someone was running some nasty water. It is going to need a manual descale. Given the extent of the rust and the need for a manual descale I decided to remove the entire steam boiler. This way I can try to remove the rust

To be continued ... Next up. Removing the steam boiler.
★ Helpful

grufromtheloo (original poster)

#2: Post by grufromtheloo (original poster) »

Removing the steam boiler

First, disconnect EVERYTHING
- remove all the sensors and hoses from the top of the boiler.
- remove the feed hose coming in from the pump on the side of the boiler
- remove the ground wires screwed down to the boiler housing, these are in front of the boiler towards the front of the machine

Second, you need to decide on one of two courses of actions for the pumps bolted to the back of the boiler housing;

1) remove the pumps from the boiler
- you have to unscrew the pump housing from the boiler housing
- there are four screws attaching each pump to the steam boiler housing
- you can get a screw driver through the access holes on the back of the machine's plastic (now exposed), there are you tube videos on how to replace pumps, they can give you an idea

2) leave them on and disconnect the electrical/plumbing
- alternately you disconnect all the electrical the pumps and feed hoses
- each pump will have two electrical connections and a white sensor, remove all these
- the white sensor may or may not be siliconed in, you may have to work at it

Third, this is the big one, you have to remove the bottom of the machine to access to drain hoses, the boiler will not come out without doing this
- you need to remove the front caster, there is a slot in one side of the plastic cap. Get a standard driver under there and pop the cap off (pic below)
- unscrew the screw in the middle and remove the know (pic below)
- flip the machine over on it's side
- remove the four screws from the back of the castor and remove the whole mechanism (pic below)
- proceed to remove every single screw you see, there will be larger fat screws and small screw. Remove them ALL.
- note there are fat screws hidden under the rubber feet (pic below)
- remove the little screw from the feet, then remove the feet, then remove the screws underneath

I am writing all this after the fact to get caught up. Will take more pics for the newer steps

To be continued...

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#3: Post by dinsdale »

I look forward to following this as today I purchased a spare BDB with most of the same issues as yours. I'm also attempting to rebuild it. Mine's bad, but at least visually, not as bad as yours.

grufromtheloo (original poster)

#4: Post by grufromtheloo (original poster) »

Fourth, remove the plastic under the drip tray, drain hoses etc
- with the full plastic bottom of the machine removed, if you look around the light gray plastic under the drip tray you will find four sets of two little screws.
- remove all these, then remove the plastic piece
- this will expose a piece of plastic holding the drain valves in place, remove the two screws holding it in (picture below) and remove it
- this will expose the two drain valves (pictured below)
- pull the retaining clips and remove the hoses or simply push them up through the hole

Fifth, it's money time
- oh, I forgot to tell you to remove the green round wire attached to the boiler housing, under the pumps at the back of the machine, you may need to cut and marrette it back on later
- flip the machine back over, correct side up
- remove the screws around the boiler facing up, there should be three (no pic sorry)
- with everything else removed the boiler should start to lift out, BE VERY VERY CAREFUL there are lots of little wires and hoses to get snagged on
- once the boiler is removed the majority of the way there should be one brown and one blue wire (on my machine) holding you back, these should be attached to the thermal fuse and the boiler heating element
- snip those wires at an ideal spot, we can marrette them back on later
- your boiler should be free (money shot below)

Note I also removed the boiler from it's housing because I am going to try and clean up that nasty rust!

grufromtheloo (original poster)

#5: Post by grufromtheloo (original poster) »

Just testing the steam boiler components now,
- thermal fuse still has conductivity so it's not blown
- steam boiler heating element has conductivity between the two exposed leads so it's not completely blow

My plan of action now that the steam boiler is removed and tested, is as follows
- clean up rust on housing, going to try a wire wheel
- descale boiler manually
- clean up rust and corrosion on probes, boiler surface, mounting holes etc
- figure out how I re attach probe wires
- order a set of o-rings, it looks like the drain valves have the same o-rings as the sensors, the larger blue sort
- remove and rebuild the steam valve

Once all that is done, I hope to to the steam boiler back in and NOT re-attach the bottom of the machine. I intend to reconnect all the plumbing and electrical to test the steam path. If the steam path works, the machine just may be salvageable. If I am going to sell it I will have to remove the solenoid to clean it up (it still works tho) and the block the steam valve and hot water connect to as they are both corroded.

To be continued ...

grufromtheloo (original poster)

#6: Post by grufromtheloo (original poster) »

I almost forgot here are the error codes I pulled out of the machine before disassembly

Error 8 coffee water flow 99
Error 9 no water in coffee boiler-1
Error 10 coffee over temp 5
Error 11 steam over temp 48
Error 12 group head over temp 5

Coffee flow, water problems. Not sure what's up here. Maybe nothing or maybe the pump is going out. The waterflow sensor was quite corroded where the electrical attaches so it may be shorted out or blown.

Over temps. I have four ideas here 1) triac board is shot 2) triac board was misbehaving when wet from steam 3) the steam leak either caused the over temps directly or shorted out ntcs somehow 4) this was a descale gone bad. Maybe a mixture of the above.

grufromtheloo (original poster)

#7: Post by grufromtheloo (original poster) »


Working on getting the steam boiler cleaned up and ready for install. Descaled it over the last two days and descaled the probes from the steam boiler. Compare the below with the pics above. The scale came off without issues but the dark (burnt? rusted?) spots didn't clean up.

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grufromtheloo (original poster)

#8: Post by grufromtheloo (original poster) »

Update. The steam boiler and ball valve are completely removed. The ball valve was a giant pain. The screw in the centre of the plastic had rusted to the point it was useless. I proceed to drill it out, which damaged the bottom of the plastic knob-core (what else do I call it?). The metal piece that mates with the valve is loose now, but I am going to epoxy it on to the end of the knob's shaft. To keep keep the knob from falling out I plan to insert the knob into the machine then drill a screw in across the shaft so the head will touch the machine's plastic. The part of the ball valve where the knob mates to got bored out a little with the drilling, but still has enough shape to mate the metal piece. Phew. I will upload pics when I rebuild so you all can see the fix.

Some updates, ball valve, all cleaned up... some of the metal is pitted from the rust and I can't be bothered to grind it smooth :)

More to follow in a couple minutes

grufromtheloo (original poster)

#9: Post by grufromtheloo (original poster) »

More updates....

Steam boiler cleaned up. One brew HX line stuck (corroded) in the boiler. Have to work on that next.

Steam boiler mount after a lot of grinding with a dremel and currently in a vinegar bath. You can see the mess this was in the picture above, look to the bottom left of the boiler. The metal was heavily rusted/corroded, surface was bubbly etc. As the galvanization is lost due to the restoration, I am going to bolt a ground to it, use small circular stickers to preserve screw hole grounding for boiler/pumps then spray paint it with high heat paint. Weeeeee


#10: Post by dinsdale »

I had the same problem with a stuck pipe in the steam boiler. After anti-scale, anti-rust and heat didn't help I pulled the teflon pipe out (which means the flared fitting is probably in the boiler) and then used an easy-out to remove the brass fitting.

I also had a problem with a leaky drain valve. The smaller O ring was damaged.