Can JB Weld fix a cracked cylinder head? See the proof!!

You know I’ve always heard that JB Weld can fix a cracked engine block or a cracked cylinder head But I’ve never seen it done And I don’t know if you have either but today we’re going to find out once and for all if JB Weld is up to the task of fixing a cracked cylinder head. There’s nothing wrong with the cylinder head on this lawnmower engine But I’m going to go ahead and basically simulate having a crack I’m going to take a cutting blade out and cut through this cylinder head, and then fill it with JB Weld, allow it to dry for 24 hours Reattach the cylinder head, and then see if it will take the pressure and the heat Additionally I have a hole in this gas tank that goes to this lawnmower I’m going to hold it up here and as I tilt it forward Gasoline is going to start to ooze out of it. I’ve got a pretty good-sized hole right up in here You can see it pours out quickly and JB weld is supposed to be resistant to gasoline So we’re going to find out if JB Weld can also fix this gas tank while we’re at it The first thing I want to do before I Cut into this cylinder head is to go ahead and clean up a lot of this buildup so I’m going to use some carburetor cleaner This is definitely clean enough, so what I’m going to do now is just cut through part of this cylinder head, and then apply some JB Weld So as you can see I’ve made a really big gash in this cylinder head and it’s so big I can easily slide a zip tie through it and This is going to be a true test for JB Weld to see if it can patch up this hole In order to make this cylinder head repair the first thing we need to do is to go ahead and bevel out on each side of this of This cut in order for the JB weld to have something to hang on to and we’re going to rough this surface up a bit Okay, as you can see there’s clearly a hole, and I’ve went ahead and beveled out around this this long gash And now what I’m going to do is mix up the JB Weld and go ahead and begin applying it into this crack JB Weld comes in… for those who have never used it comes in two different tubes and You just basically mix fifty-fifty And so what we want to do is just work this into the crack, just sort of pushing down on it And we’ll flip it over in a minute, and we’ll see if it’s if it’s flowing into the crack Again, we’re just sort of trying to massage it into the crack and this stuff is going to want to flow on us This is what it looks like now. We’ll check back in about 24 hours and see how it looks Okay, the JB weld has cured as you can see this is where the cut was at this is where I had beveled and there’s A slight indention there, but this should work very well, now I’m going to flip this cylinder head over real quick as you can see this is where the JB weld started to seep through So what I did was I put a little bit of tape down to keep it from leaking on through and draining if you will So right through here was where the crack was at and as you can see the JB weld has done a great job Of covering up this crack, now I have already pressure tested this tank. The way to pressure test the tank is to seal off the gas cap area where you add fuel and to basically put pressure through the… where it drains into the Carburetor, just add some air pressure to that to see if it holds. There was no more leaking air So I know this is a really tight seal, the question though is can it stand up to gasoline as JB Weld claims it can? Since the cylinder head came off of an engine that had low compression I want to go ahead and give this a really rigorous test I’m going to put this on a different engine that has very good compression, in fact over a hundred pounds of compression So this should give it a really good test. So you’re going to see me switch out mowers from the one I took this off of Okay, so we’ve got the cylinder head installed now I want to go and put this fuel tank on. As you can see right here. This is the JB weld This is where the crack was at right here like I said I pressure tested it I think this is going to hold fuel, so I’m gonna take a perfectly good fuel tank off of this machine and put the Repairing tank on to see if it’s going to hold Okay I’m going to spin the engine over five times Wow, that’s great compression, about 110 pounds of pressure. That is really putting this head to the test Okay, we’re about to do the ultimate test. One thing I’ve done is I’ve added an oil temperature gauge. This Mechanical Gauge, the sensor is fed right into the where the dipstick goes And I have created sort of a seal over here to keep anything from spewing out as the engine’s running So you will see this temperature rise. I’m expecting up to 160 – 180 degrees, that’s going to be our oil temperature Additionally what you’re going to see here is the temperature of the spot where you see the little laser dot. All I can say it’s very impressive results, the JB weld held up as you saw the temperatures exceeded 300 degrees Fahrenheit Additionally the oil temperature is about 190 degrees at times. I also want to say the fuel tank held up It’s leaking a little bit around the gas cap and not the actual crack itself So that’s a problem with my gas cap not not the repair, but I’m going to take the cylinder head off in a minute But if you heard there’s a little bit of a ticking sound in the motor and that was because the piston was coming in contact With the JB weld. One thing I should have done was sanded down the JB weld because it was a little too thick and Therefore the piston was hitting it. So I’ve just had this thing running at least 20 minutes and this engine runs at at least 3,000 RPMs so basically the piston has slapped into the JB weld at least 60,000 times in the last 20 minutes and it still held up despite all that impact. So all I can say is if JB weld can hold up in this engine, I’m pretty confident it can take on just about any task you have for it. I’m gonna spin the engine over five times Okay, guys looks like the JB Weld did a great job holding up. You can see some some carbon deposits on the JB weld, but there is absolutely no cracking, no issues with this at all. I am extremely impressed with what JB Weld was able to do. That tapping we heard Let’s take a look at the piston and see what it was, see where it was hitting at So you’ll notice here, there is a spot. That’s a lot lighter colored as well as here This is where the piston was coming in contact with the JB weld and as you can see the JB Weld held up really well, it did not do any damage to the JB Weld, obviously didn’t do any damage to the piston It was barely tapping it was just barely tapping the JB weld But it just goes to show the strength and durability of this product. Okay I went ahead and ground off some of the JB Weld I want to see if this is still going to work okay I think it will do just fine And I grounded off just because I want to get rid of that knock, so let’s see how it sounds and see if it’s back to normal Is that impressive or what? JB Weld Held up to a pretty tough test. You have to admit that cylinder had got pretty hot and it didn’t come apart Additionally the piston was slapping that cylinder head pretty hard And it slapped it about sixty thousand times and still did not break and so that was unplanned That was just my fault. I should have sanded that Excess JB weld off that cylinder head, so the piston wasn’t slapping it, so I admit I made a mistake there But anyway, all I can say is I am very impressed. The fuel tank held up as well, so in both tests It showed that it’s a good product. Just as a final reminder, I am not sponsored in any way by JB Weld or any of the manufacturers of the products that are right behind me here. These are all products that I purchased using my own personal funds. So my question to you today, the question today and I love reading your comments, is what have you used for making repairs? Have you used JB weld before? And is there a better product that you would like me to test for fixing a cracked or a cylinder head with a hole in it? Because I’m looking forward to testing the claims and testing the quality of these different products And you guys, I learn a lot from you You have a lot of great ideas, so I look forward to reading and responding to your comments Look forward to seeing next time on the next episode. Thank you

100 thoughts on “Can JB Weld fix a cracked cylinder head? See the proof!!

  • Few years late but I remember my grandfather back in the Philippines would mend or glue cracks on plastics with styrofoam that's melted down by gasoline. Napalm from what I've heard. But I'd always see it on cracks we had on plastic bins

  • Tired and true. That really helps to know . I new it was good , but not that good. Just goes to show flashy advertising doesn't always mean it's better. Thanku

  • You should do a comparison of J-B Weld and Quicksteel (the putty type, in a tube). I have used both over the years for various different types of repairs, and I do not recall any noticeable differences. Both are excellent. But, I never actually tested and compared them.

  • This is exactly what JB Weld was made for. My father worked for the engine repair shop that developed it back around 1950 in Sulphur Springs, Tx.
    Also, if you can find it, there's a material called pr-1422 that is designed for sealing airplane gas tanks. Not sure it can be found outside the military, but we used it at NASA for different purposes on the Space Shuttle. If you can find it let me know, I'd like to get some. Awesome stuff.

  • I once Jb welded a cracked head that was leaking radiator coolant. So yes it's very strong product. Great video.

  • So my pressure washer has a small crack on the pump, just before the long pipe to connect sprayer. Should I try it before spending 100 on new pump

  • I’ve used j&b on a 2004 Hyundai head gasket…. you should redo the test with the proper sanding and see if it last a full hour

  • he just made an overly large singh groove an amricns name isa groove 2 but i dont bremember what. it was supposed to help combustion . did it to a scooter head but did not notice much

  • I haven't watched this for a long time, and I must say I'm very impressed with how well JB Weld held up. 🙂

  • To prevent the video level changes use manual iris. You see the hange easily when your hand w white glove is in the picture.

  • JB Weld worked extremely well on the aluminum housing of my Mercedes automatic transmission that cracked and leaked fluid. I sold the car in 2003 and the buyer still drives it.

  • I repaired a engine block with it before and worked great. I am curious, about the longevity of the head repair. Did you continue using it? if so hows it doing?

  • I had a crack in my (plastic) intake manifold on my Saturn SW2 that was leaking coolant. I cleaned and buffed the surface around the crack and a piece of pvc, glued the PVC on with JB Weld, and voila, no more leak.

  • JB weld may be gas/oil resistant once cured, but it will not adhere if there is gas/oil already present. I can't remember if JBWeld makes it or not, but there is a product called WaterWeld that is a more putty form that will adhere in the presence of water or oil/gas. Might want to check it out!

  • Most people don't know that the JB in JB Weld is the name of the creator of the product. Before he invented JB Weld he used to work on the streets in New York and people called him Jizz Boy as his nickname.

  • I had never seen a craftsmen tool green color with yellow letters?🤷🏽‍♂️ beveled yes, but how are you gonna get penetration?

  • Hi sir I've been using aroldite for many years and have found it to be a great product it's petrol resistant and heat resistant but it takes twelve hours to dry I'm very impressed by jb weld I will be getting some of this for future repairs many thanks for your video best regards Tony

  • my first job was at a diesel mechanic shop 25 years ago. One guy who worked there, and was probably the best mechanic, sent me to NAPA with instructions to get a tube of fastweld and if they were out get JB weld. Whenever I came back he used the tube of fastweld to fix a hole in an engine block. It was an awkward shaped hole but it was probably 2" at the widest spot. I don't know how long the engine lasted but the guy doing the repair was one of the most reputable mechanics around and i could tell that it wasn't his first rodeo with that type of repair.

  • Pioneer devcon is the only product here in Phils. I want to see if it works as good as JB weld.

  • JB Weld is the only product that friends have told me works, if applied correctly, on car engines in the same fashion.
    After seeing this test I don't think that there is another product that works this well.
    There is a product called liquid Steel however that I've never heard or seen used on a automotive engine or cylinder head.
    Arc Welding might be the only thing better.

  • I don't know about a lawnmower head, but I do know it'll fix a Yamaha motorcycle block. Great video

  • Would you please do a comparison between UV curable glue/adhesives? There are not that many of them that I know about. Maybe you can find more, which also would be very important to me. I have used two different ones and I've definitely seen differences which most of the people reviewing them on YouTube Don't See. They also don't understand that you can't connect two dark surfaces together like a regular adhesive. If UV light can't get to it then you can't cure it. You have to put a layer on one side and cure it first and then add more UV resin/glue/adhesive, or what ever you want to call it, to both sides so now the UV light can go through between the surfaces through that already hardened first layer and cure the fresh later. I have compared the two using thermal camera and I do see that they both heat up just the same during the curing. Super fast and very hot. But after curing, one had better surface adhesion than the other. I haven't really seen a good comparison here, that's why I'm asking you to step in and do it the right way like you always do. I think your videos are very informative and they take the guesswork out of my projects. Thank you and keep up the good work.

  • 9:36 – it appears that the head gasket is torn. How is it you were able to get 110 psi in that condition ?
    Great vids you put out, keep up the good work.

  • I have a plasic fitting on my carburator on my riding lawn mower. Its actually where the gas line connects to the carb. It broke and of course you cant buy it. I jb welded it and have never looked back. The stuff is amazing!!

  • I have a jb weld story. I welded up a oilpan from a cat diesel engine. It came in full of jb weld and not leaking. (Cast aluminum) I couldnt believe that pan was bone dry so i wondered why bother fixing it? But the customer is the boss so…

  • JB weld is a great product. My most impressive repairs using this product have been radiators. Many others as well. Thank you for all the videos

  • I used it to weld a crack on the bottom side of the oil pan on my 2002 Volvo v70 when the engine had 19 k miles back in 2003 I still drive this car today at 200 k miles. Amazing stuff.

  • I really like your videos except the only band part is I've been watching them all the along fortunately I am working on AJB Weld project fixing a leak in my radiator I really appreciate your videos very a Foreman of in your doing a great job very fair non biased reporting souls like I'm watching a commercial good job buddy thank you

  • At 9:35 when you rubbed your finger on the metal, the scored siding where the bolt hole is moved. Just curious what's up with that piece since that spot wasn't JB welded. Thanks for the awesome videos btw. We all use the products you test and we all wonder what's the difference. Finally you are giving us the answers so thank you for everything you do!!

  • Many years ago (1976) i used JB weld to seal my exhaust pipes to my cylinder head on my 650 BSA motorcycle, because of wear and vibration, the pipes would not seal properly any longer. After using JB weld the pipes sealed perfectly and withstood many years of hard use, without failing. I eventually sold the motorcycle with the JB weld still in place, still sealed.
    In my view, there is no better product for emergency repairs, especially on engines.
    Thank you for all the experimentation you do, i watch your channel often.

  • Great product and glad you tested it. Another great product is Kwikwood made by JB Weld. Replaced hinges on kitchen cabinets. New hinges had a screw hole pattern so close to previous holes that drilling the new holes would compromise the holding ability of screws on the new hinges. Applied the KwikWood to the old holes and let cure. Drilled hole pattern for new hinges, sometimes making contact with the KwikWood.
    KwikWood held in place and more importantly, the screws held tight. Love the products this company makes and I applaud Project Farm for testing these consumer products.

  • JB Weld saved me on a repair job where antifreeze was shooting through a small hole on the top of the engine. It really saved the day for me.

  • about 30mil out of Ft Lauderdale I had a spark plug blow out I put JB Weld and put it back in and use the moter this way for 3 year.

  • Amazing stuff. My son fixed a cracked block on a garden tiller with JB Weld. He is less experienced than me and I told him it was a waste of time. The thing held up for years and he didn't even do a very good prep job on the crack. I'm now a believer.

  • I do retail store repairs and once had a metal light shade that broke and the only way to repair it was to weld, but then I thought to use JB Weld. Worked perfectly.

  • I had a 72 Challenger, kicked something up off the freeway & punctured the gas tank. Gas was draining out like a petcock. So on the side of Hwy 99 I mixed up some JB Weld dipped a sheet metal screw in it & screwedit in the hole. I lost maybe 1 gallon of gas and that held for the next 2 years that I had the car.

  • I'm wondering if a guy could use it to fill a set of dish pistons to make them into a custom set of flat tops for more compression, I bet it would work. Lol , is a definite product to have around when you live away from parts store or don't have time to shut something down to tear it apart, I've used for many years on everything from the cars to dirtbikes and mowers. The plastic jb works very well and I'm really impressed with the high temp red gasket sealer , I recently used it on chrome headers on 355 race motor , we put those headers on a few months ago with high temp red and have cruised that motor turning it very high rpm with no leaks .

  • JB Weld is great stuff. I put it on my radiator when I developed a leak in the tank on the top with a fairly high pressure radiator cap while I was traversing the California Desert at around 115 degrees Fahrenheit. I held up for several years after the patch as I was moving to Colorado. The car was finally totaled at a stoplight by a semi, but the patch held tight the entire time. I also repaired a cracked transmission case on my Harley and it held and never leaked for years. I was told by the shop, it was a goner, and couldn't be repaired. They were wrong.

  • It's great stuff. I use it a lot. Sandblasted metal with pinholes gets a coat. I bet you could make a whole cylinder head with it. It can be drilled and tapped no problem.

  • I would like to see you fully port & polish a cylinder head then compare it to a non ported & polished head!

  • Try Marine Tex epoxy sometime. Been told by a guy that he used it to fix a cracked block, and cyl head. Its machineable. I used it to fix a large gas leak on my holly carb on a marine application 4.3l motor.

  • OMG, love that sigh at 2:10, when you admit to yourself that you just cut a hole in a cylinder head on purpose!!! Keep it up, love it!

  • I had a customer one time in my shop that was going to the local lake and needed a temporary fix on his Toyota pick-up radiator neck that had so much corrosion from the anti-freeze not having been service that the neck came away from the upper tank. Plus he had little money. We put JB weld on the neck and he went to have a sandwich and was gone about 3 hours. We rattled the cap so the engine had coolant flow but no pressure and told him that in 24 hours to go ahead and check the fluid and let it pressurize and check for leaks. He came back for something else while traveling through ………….. 2 years later. And the JB Weld temporary repair was still there. He never had the radiator repaired or rodded out. So we gave it a little black paint job and off he went. Tough Toyota Tough JB Weld.

  • I seen a video where you dis flex seal, job weld gorilla glue and something else. I was surprised that with the gorilla glue you dis not wet it as that is what activates it . I by think this is what made gorilla glue do so poorly in your test.

  • In the early 1970's I swapped for an 1952 Pan head Harley that a dim dot was riding on a gravel road going up a hill and dumped it on the carburator side. About a quarter mile below the hill the road crossed a creek so They tied a rope to the back of the frame and drug it down there to put out the fire. All this broke the stock carburator manifold off the head. I was able to get it going again with an O-Ring adapter and JB weld. Yup.

  • Ive used it on high preasypower steering line covered it with fiberglass and jbweld hold up 6 monts

  • About 20 years ago, I used JB weld to repair an aluminum intake manifold on a Toyota 4Y engine. The carburetor mounting studs had vibrated loose/wallowed out the threaded holes.
    Another tech had drilled/helicoiled the holes, but they did so WAY off center.
    As a result, it had a bad vacuum leak.
    I removed the studs, pulled out the Helicoils, and used JB Weld to fill in the holes and hold the studs in place.
    It worked well.

  • I own a jeep cherokee and on the 2000 and 2001 model the heads are known to crack, mine did. I used JB weld to repair the crack and have been running my jeep for over six weeks now with no coolant going into my oil. worked for me! thank you JB.

  • I've got a 2 stroke 125 bike engine with a whole the size of a little finger nail in the lower case on the intake section which the carbuerator mounts. Will JB be suitable as a filler do you think? Threaded hole within the gap that needs filling, that leases out to the stator plate on the opposite side of the engine case.

  • 82 reliant k in high school was pissing coolant out headgasket hitting radiator. JB weld held up till the end of the car…

  • Hi there. Great video, thanks! I recently heard that Weldbond is a pretty good general purpose adhesive. I think a video showing its performance in different use cases could be interesting!

  • I've commented this before
    I'd like to see a test between JB Weld and PC-7 and Marine grade PC-11 and any other 2 part epoxy you want to add to the test.

  • i know this is two years old, But at the end of the video you ask, what else is out there?

    I've used Belzona with Great Success, Even built up a worn shaft, turned it to size and re-cut a key way in it to mount a pulley

    It is very pricey though.

    and of course from my previous Comment, PC-7

  • Bruh wtf. I tried using it to fix a pair of glasses which I had stepped on and it didn't hold. Even after letting sit for 5 days.

  • The gas tank I had no problem with it holding up as I use JB for carb modifications. The head, now I am impressed!

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