Introduction: Clean a Bunn NHBX-B 10-Cup Coffee Maker Properly

About: I have always been tech support for just about everyone. I am an Autodidact. There is nothing I can't teach myself. I was a Auto Tech for more than 20 years. I was ASE Master certified. I was in the top 10 div…

If you have one of these coffee makers I am sure you are like me - You LOVE the maker because when clean it can make a full pot of coffee in 3:20. I have three of these makers ( yes I have almost $280 invested in coffee makers, LOL). I have one in the kitchen and one in my office. The third one is for when one needs service. If you have hard water you know the struggle to keep a maker clean. There are only so many times you can run vinegar through it to clean it effectively. Then it must be serviced to correct it.

For reference the little plastic de-limer tool that ships with the machine is the best part of worthless. I have replaced it with a big 24" zip tie. Wider, stiffer, and far more effective.

You will need

1 - 12" #1 Phillips screwdriver to release the top reservoir.

60/40 solder and a soldering iron

Wire cutters/strippers

Small (like tiny) rubber mallet to shock the tank to release the build up

Some sort of spudger- Preferably a small plastic one. This is the for the top rubber seal for the inlet from the reservoir. You can use a flat tip screwdriver to do this but you must be careful not to damage the rubber seal.

Clear silicone. Do not use anything else. Use only silicone as other sealers may interact with the seal material turning it to mush and destroying it.

Windex or your favorite cleaner. I recommend that you stay away from real nasty cleaners and chemicals as you may forever ruin the taste of your coffee in the unit.


This may be above your skill level.

Step 1: Draining the Unit and Cleaning the Reservoir

Drain all the water from the unit. To do this remove the top/lid of the machine by grabbing the edge of it in one place with your fingernails and lift. After this lid is started it will come right off. Don't be rough with it but don't be afraid to pull a bit. It comes off pretty easy. Now remove the white rocker valve arm from its mount. This should lift straight up. Now flip the machine upside down and let it drain. The draining will take about 5 minutes as it glugs and has no inlet for air when flipped over. While the unit is draining clean the top lid and the valve arm. Make sure that the seal on the arm is clean and free of build up.

Once drained clean out the bottom of the reservoir. This stuff should come off pretty easy. Once you have it clean you can follow up with the spudger to pick off the hard to remove stuff.

Chances are real high that yours will look as nasty as mine when you have it open.

Step 2: Open the Bottom of the Unit

On the bottom there are two screws, remove these and the bottom will come off. The wires for the hot plate will be connected still. Here is where colored electrical tape or a zip tie is helpful to mark polarity of the hot plate element and other items later in the dis-assembly. Once you have these mark you can cut them to free the bottom of the unit. I have no idea what the result would be if the hotplate was hooked up backwards.

IMPORTANT - This is also where you want to take lots of pictures so you can figure out the connections later. Where wire colors are the same mark them with your colored electrical tape or zip tie..

Step 3: Remove the Top Reservoir Body

Here there are 4 screws to release the top reservoir. You will need a 12" #1 screw driver to do this step. Once you have the four screws out you lift the reservoir off. These are only accessible from the bottom of the unit. Look up into the four corners of the unit and at the top you should see 4 screws. Remove these. When you take the reservoir off you will see the temp sensor and the top seal. Chances are that your seal will be covered in build up like mine.

The seal for the inlet and the temp sensor will need to have the build up cleaned off. This should scrape off easily with the blade of a screw driver or spudger. I use a plastic spudger I bought on eBay for a dollar. Once you have this clean use your plastic spudger to lift the sensor and rubber gasket out of the tank.

Step 4: Remove the Water Out Put Hose

Remove the sprayer nozzle then remove the nut that holds the outlet elbow and the elbow will come out easily. You should not have to force any part of this. This part of the disassembly should be obvious. Don't get to wild with this part as these can be brittle if the are old. Define old? More than 5 years old with non stop coffee making all day.

BTW I drink coffee right up till I go to bed. You will also see that I used zip ties to hold the hose on when I was assembling the unit. When doing this you have to pay attention to the position of the zip tie lock to make sure it will not interfere with the reservoir when you go to install it.

Step 5: Pictures of the NASTY Build Up

Mine as you can see was flat nasty. This was caused by the coffee spilling on to the unit and being allowed to cook off. This build up is flaky so it will come right off with minimal effort. Notice that the metal base is galvanized steel so the residue will not bond to it.

Step 6: Disconnecting the Wiring

Here you will have to remove the wires from the heating element so that the tank releases. Then remove the insulator (square tube) for the heating element. Clean off any build up on it. After wards there are two white holds to remove. These hold the tank up in place when assembled. To remove these you will have to remove the main power switch. Once the switch is out the rest should come out easily. The switch comes out buy squeezing the releases together while you push the switch through the opening it is installed in. You should not have to pull the wires on it to get the tank out. Once you have the switch and the supports removed you should be able to lift the tank out easily.

IMPORTANT - Do not cut the two power wires that go to the sensor. These are cloth insulated.

Step 7: Removing the Build Up From Inside the Tank

Here I used a small rubber mallet to tap the tank to knock off the build up inside the tank. You can see inside the tank through the inlet and judge when you think you have gotten all the debris loose you can start shaking that tank like a maraca to remove the debris. By shocking the tank like this it should remove almost all of the debris including the stuff stuck to the heating element. Check the pictures and you can see the larger stuff.

Look at the picture of the debris on my work bench. It will surprise you on how much will come out. My unit was exceptionally bad.

If you are replacing the heating element now is the time. The top of the tank comes off by prying the tabs that hold it to the tank seal. Once pried away it should release the top giving you access to the heating element. On each leg of the element there are nuts, remove these and the element will come out. When installing the new element make sure that the seals are spotless. They will leak if there is any debris on the seal.

Step 8: Reassembly of the Unit

I do not have pictures for this part of the process. It is basically the reverse of what you did to take it apart. When connecting the wires you cut earlier you should solder the hot plate wires and use shrink tube to seal the connection; I am assuming you know how to solder properly. If not there are several Instructables here that show how to do it right. The other main wires should be connected with the appropriate wire nut or a waterproof crimp connector. These are the ones that you crimp and then heat with a hairdryer, heat gun, or open flame. The connector shrinks down and releases the waterproofing glue at the same time making a perfect connection that will not fail in the future.

IMPORTANT: When installing the top reservoir (where you pour the water in) put a small amount of clear silicone at the inlet on the rubber gasket that holds the sensor. Sometimes the heat from the tank distorts the bottom of the reservoir making a poor seal. Skipping this part could make the unit leak when being filled. Make sure that this is given time to fully curing before putting the unit back in service. I give it 24 hours. I suspect that it would be usable in 12 hours but I would rather err on the too much time.

When cleaning the unit used Windex because it removes the film on the outside very well.

Once you have it all back together I would recommend running a 50/50 mix of water and vinegar through the pot for two cycles and then do the normal rinse out. I usually run 5 pots of water through after the vinegar and water mix to make sure the pot will be totally clean.

On the first pot the coffee may taste strange or stronger. This is because the heat is actually getting to the water like it should. Plus the sensor is clean so that it will read properly. If this happens do not panic, in 2-3 pots it will return to what is considered normal.

When the machine is clean I use two filters (Mr. Coffee) to slow the brew process just a few seconds which allows the hot water to sit in the coffee ground just a bit longer. As for total brew time doing this is it not really noticeable.

I hope this was of help to you in getting your coffee maker back in service. Time to go make coffee.