J-B Weld ExtremeHeat

I purchased this item to repair an ash fettle in an old Vermont Castings wood burning stove, and it completely exceeded my expectations outlasting an entire season of direct fire contact. The fettle was cracked into two pieces and a prior owner had drilled two holes on either side and tried to connect it with an aluminum "bridge." The repair interfered with the door closing, so I needed to seamlessly "weld" the two cast iron sides back together. Before going through the trouble of taking it to a welder and paying to have it repaired properly, I took a chance on this J-B Weld ExtremeHeat. I used a Dremel tool with a fine grinding stone and cleaned up the two broken faces, along with about 1/4 inch of the area on either side of the crack. Following the advice of another review, I then took a cotter pin, stuck it into the chuck of my battery powered drill, and used that to thoroughly stir the J-B Weld in the container (this is a one-time use container... once opened and stirred, use it and toss the rest). After stirring for just under 2 minutes, I immediately applied it to the two surfaces, pieced them together, and then spread a little more on either side to ensure a supported bond. I then set the item on a flat piece of cardboard to cure for 2 days. (NOTE: you have to support the joint while curing, because the J-B Weld provides no structural support until completely cured. While wet, the item will just fall apart again if the pieces aren't otherwise held together.) When it was done, I replaced the fettle and lit the first fire of the season (crossing my fingers at the same time). Several months and probably 100+ fires later, the piece was still holding strong like the day I put it in. The fettle sits right against the fire, and many logs have rolled into it while it was extremely hot, with no noticeable damage whatsoever. I would absolutely recommend and use the J-B Weld ExtremeHeat again on future projects. As long as the proper preparation is done, and you follow the instructions, it's an awesome product!

I used it to repair a crack in a cast iron oven top stove grate. Quick and clean fix and good value for the money. Highly recommend.

J-B Weld to the rescue! My 2004 Nissan Xterra V6 developed a leak at the exhaust manifold side of the pipe connecting the EGR valve to the exhaust manifold. The tell tale sign was smoke (like cigarette smoke) coming from the base of the pipe to the EGR valve and the smell of unburnt fuel. The ideal solution was to replace the pipe but there is no room to get to the hold down nut anchoring the pipe to the manifold. I decided to use J-B Weld 37901 to seal the leak. I had my doubts but after applying three layers of this stuff, one day at a time, there is no sign of the smoke and smell. This was not easy to apply because of the tight space but it worked well using just one finger (mechanic's gloved) tracing around the pipe connector to the manifold. It dries quickly and spreads slowly to keep the form. Time will tell if the fix will hold for at least a year. Check out the pictures.

If you use it for deep hole filling it takes more than an hours to set, it is strong but not that strong you can brake it with your fingers, if is applied on hot surfaces it tends to shrink.

I used JB weld extreme heat on my outdoor wood boiler. The cast iron door had a nickel sized hole and the steel that the door closes against had deteriorated because of the hole in the door. This stuff worked with minimal effort. The steel and cast iron was cleaned to the bare metal with a wire brush on a drill to insure adhesion. The high heat has not affected the JB weld whatsoever. Highly recommended.

I followed the instructions on this product well and while it did perform better than the squeeze bottle J-B Weld high temperature muffler repair, this product still cracked under frequent hot-cold cycles on an exhaust system. It did last longer than the dedicated muffler repair product which is why it's getting at least the 3 stars.

I prepared all surfaces with a Dremel with and wire brush attachment. All surfaces became shiny, clean metal. First impression of the product - very small. It says 3 ounces, but that's by weight, so obviously much smaller than 3 fluid ounces. That said, it also weighed less than 3 ounces on a tested scale even with the tub included, so I feel like I've been cheated. Next point: it was a thick, dense paste, not the liquid you see on the videos. I would guess that was because the foil was damaged or not properly sealed. It was the correct color: separate tan/black before mixing and cement gray after, but mixing took quite a lot of effort, because it felt like nearly cured cement when mixing. I did each step quickly, with no time between opening, mixing, and applying, so as not to allow it to cure prematurely. Being a nearly-dry cement consistency, It didn't want to adhere at all when applying it to the clean metal. I forced it to stay on by placing wood objects to keep it in place. I waited around around 30 hours. My setup to keep things in place worked. The epoxy became completely dry, but not strong at all. The very light metal parts separated with almost no effort beyond the parts' own weight. I was attaching a very light heat shield to a vehicle floor. The heat shield had two good bolts already holding one side and middle; I was just attaching the other side where the stud had broken from the vehicle floor. The bond didn't even last long enough to give the vehicle a test drive. The epoxy was just barely stronger than a dried sand castle. Strong enough to hold its shape, but noting else. I can crumble it with my fingers despite it having been given time to dry completely. In closing, this job took a lot of time and effort, and it was quite frustrating and discouraging to see the results. I will attempt to return this to the seller. Regular JB Weld has been good stuff, but this extreme heat version turned out to be a total failure.

It’s awesome as soon as it dries you know you have a bond