J-B Weld 37901 ExtremeHeat High Temperature Resistant Metallic Paste - 3 oz

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!

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.

worked great

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.

Used it to fill in rusted out gap on an oxygen sensor bung that was leaking air into the 02 sensor and causing false reading. That was causing the check engine light to come one. You really have to prepare the surface. I used a brass wire brush to scrub out loose rust of which there was plenty. I was wearing chemistry lab goggles and my face was covered with rust afterwards. Then mix the stuff. Yes it is one use you are mixing an epoxy glue. I used nearly all of it anyway. Mix it thoroughly and let it set up, it thickens fast and is easier to lay on when thick. When you first mix it the stuff is quite runny. I spead it on with a wooden coffee stirrer stick. This was a tough application because it was the exhaust underneath the truck so gravity is working against you. I managed to get one layer on and laid on some more. The putty is kind of self leveling which is good. It kind of drips but by that time is so thick it still stays in place, mostly. The O2 sensor was still attached so I was repairing the bung around the gasket of the O2 sensor and trying to pack the stuff into the gap. Then I let it sit for the full 24 hours before driving, to allow it to cure fully. The truck has 2 catalytic converters and the original owner replaced the passenger side one more than 50,000 miles ago so I know the other one is getting to the end of its life. But getting air into the 02 sensor due to rusted out fitting contributed to the problem. So far so good I drove it 3 days no check engine light and the exhaust putty is holding up so far.

Used on two different occasions. Works OK if you really prep the surface well. If you don't it will come right off. Better to use on heavily rusted or rough surface. Do not use on smooth/clean surface.

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.

Finishing a project in the workshop, I found this paste really helpful for fixing metal parts exposed to high temperatures. It works well and holds up where other adhesives might fail. 😊 Definitely something to keep around for serious repairs.