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What causes cracks in the firebox?

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  • #16
    I have followed the deflector placement advice ever since I read it and have never had an issue. Solid advice and no reason not to follow it.


    • #17
      Just got replacement fire box and fire ring for my Big Joe. Both now have expansion joints cut in them.


      • #18
        Unfortunately that isnt the end of it. I got mine in October and its developed a crack despite having the expansion joints in them (my crack is actually running down from the fire ring and connecting two holes, opposite the expansion cut. Opened a ticket, awaiting response.


        • #19
          Originally posted by 997cab View Post

          From another web site:

          Mods or John, please feel free to add whatever to this post and possibly make this a sticky. There are several new members buying KJ and not knowing deflector placement during certain cooks. I have made this post as an educational tool for members who own a KJ.

          I too have been the victim of a cracked fire bowl. It baffled me as I thought that I did everything right. I followed on line videos and others directions and still cracked two bowls. I really was starting to believe that it may have been an issue with ceramics, however, other members were not cracking bowls..... I began thinking that maybe it was something that I had done or was doing to cause this???

          So after replacing my two bowls, and since purchasing another 3 kamado Joes I have learned through trial and error and have not yet cracked a bowl in over a year and well over 200 cooks on my kamado's. A few simple tweaks and I am happy to report that I am crack free in over a year.

          So here are some things that I have changed:

          when shutting down the grill, I shut the bottom vent and leave the holes open, gradually closing them to allow for heat to escape when the kamado is hot. I always wondered what the sudden closure of both vents would do with the heat continually building when the fire is snuffing out.

          For different temp cooks I place my deflectors in certain positions:
          • 300 or less - deflectors in low position
          • 300 to 500 - deflectors on top of xrack (sits them a bit higher allowing for more heat to escape the fire box)
          • 500 and above - deflectors on top of the grill in top position (creating max room for heat to escape the fire box)
          • Nuclear for high heat burn - deflectors separated resting on top grill so two half moon resting on the top grill not joined together
          • for indirect cooking, I double stack the deflectors to one side, allowing for 2 zone cooking and free movement of heat. (2 zone for me is usually between 350-400)
          The most common time that I hear of a bowl cracking is during a pizza cook. Here is my set up for pizza now, not saying it is the right way, but it works and no more cracks. I put the deflectors on top of the grill with copper T plumbing fittings and the pizza stone on top of the fittings for air flow.

          Anwyas, this is not the gospel, and sometimes things just fail.... but a few small tweaks and you may have similar outcomes like I have had over the past year

          You, John Setzler, wsmith6.2000 and 11 others like this Unlike this

          Thanks for the heads up. I'm on my third firebox in two years. So I will try to follow the advice in your post to see if I can put a halt to the cracking. KJ should send out this info to all new and old users to try and prevent this cracking from happening.


          • #20
            I have always put my deflectors the highest i could go with pizza cooks and still got a cracked firebox and base. In fact, I have only had my Big Joe for 7.5 months and have filed 4 warranty claims, 3 of which are cracked ceramics and the other my hinge.
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