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

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 Replies to “Can JB Weld fix a cracked cylinder head? See the proof!!”

  1. 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!

  2. 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.
    https://www.pcepoxy.com/wp-content/uploads/2017/03/Standard-Product-Catalog.pdf

  3. 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.

    https://www.belzona.com/en/products.aspx

    and of course from my previous Comment, PC-7

  4. 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.

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

  6. Great video! I have used JB weld on the 20 to 32 cc 2-stroke gasoline engines in my RC airplanes, to:

    – Add a fitting to the carb metering plate to equalize pressure
    – Block the hole in a choke butterfly
    – Fix a cracked cooling fin

    Not as impressive as patching a cracked block, but now that I know I CAN…

  7. JB Weld is indeed awesome stuff. I once used it to repair my oil pan after it was damaged when I ran over curb/median in the road.

  8. i replaced a leaking manifold gasket with a breakfast cereal box cut to shape with silicone sealant on both sides, went on forever, perhaps that is something you could try for a cylinder head?

  9. What I would like to see is, and I may just do it myself to find out, is will JB weld patch a hole in the case? I have a 10 hp Horizontal shaft Tecumseh that threw a rod. It punched a 2" round hole in the side of the case near the electric starter. I wonder if a piece of metal to cover the hole, with JB Weld applied under and around the patch will be able to withstand the heat and oil of the running engine?

  10. Not a good test at all 1 you didn't fill the gash you made grinding 2 you left a lot of excess JB in combustion chamber

  11. Several years ago, my old boat ended up with a cracked block. I am not sure what the dealership fixed it with, but whatever it was, it worked, the engine never leaked water again. On another note, one of your other videos reminded me of one of my dad’s stories. Someone took a New Plymouth off the rack during his crews lunch. They had drained the oil just before lunch. The “idiot” who took the car sent three rods through the left hand side of a 383 V 8. He got 8 miles before it happened. He is also lucky he didn’t kill himself as the transmission also exploded into 50 or 60 pieces. I enjoy your videos.

  12. My wife hates that I found this channel. “What’s that, honey? I was watching someone cut apart a perfectly good motor and glue it back together”

  13. JB Weld has saved me on many occasions. It's great for fixing studs in place when they have been stripped out. It has saved me a lot of time and money.

  14. thank you so much for these videos! I am hoping its gonna hold my gear shifter casing together. My shifter housing on the stiring wheel broke in half and i dont have a thousand bucks to fix it so i am hoping this is gonna work! I am thinking if it can hold up to all that pressure, it should be able to hold my shifter housing together! wish me luck!!

  15. Scratch that idea about brazing the piston head with a hole in it. Got it got enough with a map torch and did a nice brazing with aluminum rod. The 18.5 hp Briggs ran good for all of good 25 minutes then came the white smoke from the brazing not holding and oil getting into the combustion chamber. Just ordered a new piston rebuild kit. I did not want to tear the engine down but have to. Keep this lawn mower going. Don’t want to buy a new lawn mower.

  16. The valve guides were completely worn out on my old 4 wheeler but a new head cost more than it was worth. Shop said the guides were not replaceable. I drilled them out oversized and jb welded in bronze bushings….still running 4 years later

  17. One reason for the compression being so good may have been due to the layer of JB weld decreasing the static volume of combustion chamber thereby increasing the compression ratio.

    Agreed that JB weld is an amazing product as it secured a hose barb to a side tank on my 1991 Lincoln.

  18. The trick to fixing a crack is to stop it from propagating. The best way to do that is to take a drill and drill a small hole just at the end of the crack, or perhaps slightly beyond so that the crack will propagate into the hole. Its the way they fix bells when they develop a crack. The round hole spreads the stress and the crack wont propagate further. Without that all the stress concentrates at the point of the crack and it continues to grow. Getting it into the crack can be a problem. Using a thin product under a vacuum in a vacuum oven or chamber can help if you have one. Compressed air on one side can work if practical. (Like a sealed container that you can apply it on the inside surface of.) Otherwise open it up with a dremel.

  19. I got a camp stove which was damaged in the mail. The cast aluminum burner was cracked though not broken. Would JB Weld fix the crack? My camp stove runs off a propane tank.

  20. I had a Porsche about 30 years ago and the transmission had a big crack on the side of it. I took it to a welder and he stated that the Porsche transmissions were were cast from magnesium and an aluminum mix then told me sorry I can't weld it. A rebuilt transmission at that time was about $1500 so I cleaned up the crack and applied JB weld and it worked but after about 3-4 months the oil would get under the JB and it would start to leak again also the crack was about 4 inches long. I did this about 3 times before buying another transmission. For a quick fix I love this stuff.

  21. I am a huge fan of your videos! I have used JB Weld wood filler and was amazing! I repaired my pool pump with the JBWeld Water weld , which had a huge crack in it, and it is still working today like a champ! Thanks for the videos!

  22. JB Weld makes a white plastic putty that I used to repair a cracked pool skimmer assembly. It was wet and full of water and the job weld went on and cured up and it is doing an amazing job. My skimmer was leaking so bad before I would have to top off my water every week and now the water has held its level for a couple of months now with no leaks. JB weld is a great product.

  23. My JB weld story involves my 06' SkiDoo Summit 1000 breaking off a piece of piston skirt and getting pinched in between the crankshaft and case. Causing a rather large spiderweb crack (low rpm incident so didn't blow completely through the case). It was welded and extra sealed with JB weld. 600+ miles later and close to 9000rpm on several occasions and still holding strong. 10/10 would recommend.

  24. Welding a new chimney pipe through my outdoor wood boiler. Couldn't get quite enough heat into it due to welder size and welder skill. Numerous pinhole leaks. Decided I wasn't chasing them all day. Three packs of jb later and we'll see how it holds up with180 degreee water around it. Old burner and worth the try.

  25. a broken flywheel on a Tecumseh lawnmower engine -it broke off the magneto mount. I jbwelded the mount back -let cure a week and put engine back together and its run 5 years now. I haven't had luck using it to fix leaking quantum tanks tho. the gas eats tru it

  26. I restored a 1965 Mustang when I was a teenager. The rubber that was pressed between the pulley, (inner disc and outer ring), on the harmonic balancer, had rotted, and the harmonic balancer came apart in two pieces. The V belt also ran the alternator, the water pump, and the cooling fan. This was about 1980, and the harmonic balancer was not available from Ford, so it was junk yard, or repair. I glued it 3 times with Devcon metal epoxy. The best that did was 2 days before it melted, and the centrifugal force destroyed the bond. I then tried JB Weld. It never failed. 238,000 miles later was still intact.

  27. Another repair I just remembered, my air compressor has a rust hole in the bottom of the tank. JB Weld has sealed that hole to 110 PSI for 5 years now. I'll let you know if it ever fails.

  28. Knocked a hole in a dirt bike engine block( on the bottom). JB weld and back in to the cliffs and creek bottoms. Again later on a cracked exhaust manifold on an old 1978 Chevy Blazer . Buddy used it on a rotted out dirt bike gas tank. The old steel tank on a Kawasaki. It started seeping in a couple of months. Seeing this all as a 9 to 16 year old kid.

  29. Hey man just found your videos today and i dont often subscribe to channels even ones o really like idk why but that doesnt matter you just gained a sub. Also i dont know what your range is in testing products but one that kinda seemed in a similar catagory was Armor All i know personally that its awesome its also expensive i also know stuff half the price seems to work just as well. My question/sugestion is this are they comparable, do they both provide the same quality of surfactants that the weather has deteiorated? Or is it just a looks good at first but fails with a little time? Also i would like to see the claims tested. Does Armor All really replace these surfactants? What i can tell you is if you put it on rubber/plastic regularly it will prevent deterioration not only that but dry brittle time worn surfaces are brought back to life with it(try it yourself on auto molding, the place between the hood and windshield, the #1 spot its very nessicary is where brittleness has become a problem such as windows weather strips and windshield wipers)

  30. Also you are a great spokesperson (i know your not sponcered) you could be the next billy mayes because who knows the other weirdo that tried to take his place..? Nobody!!! But you would be perfect. Lile a cross between billy and mr rogers… A great combo if you ask me lol.

  31. Just used JB Weld (original) to patch up a leaking core (freeze) plug on my 1995 S320 Mercedes. It should get me through the two weeks or so until new parts come in! JB is great stuff, it really works best as a stopgap measure as opposed to a permanent one.

  32. I used jb weld on a rusted mower tractor wheel hub that rusted through its welded seem. Cleaned it and gooped it and let sit for two days. It holds air perfectly now for three years!

  33. I think a test between JB weld and the Harbor Freight HFT Epoxy Super Weld would be a great test. Is the money with the quality? I think so…but..

  34. Wao !, you sir are an open book of learning on video, every single video from you, I always learn how to do something different , thank you very much. By the way, even if the video is about a crazy idea, you're teaching ways to do something in an organized manner, so I find them very useful as well, thanks again….

  35. I have used JB weld to fix a crack in a cast-iron engine block. Worked great. I also used JB to fix a small hole in copper tubing on the high pressure side of an AC unit. Both applications worked fine. When using JB Weld, make sure your area to "Weld" is totally clean & dry. I use rubbing alcohol to clean.

  36. I was distracted for a few and when i looked at the screen again my first thought was: WTF? Is that a mould for those dangly bits some ppl like hanging from their truck?! Oops 😁

  37. I know i am years and years late but!! It would be so awesome if you can cast a JB weld head and compare that to a regular head :D. Mayb start a series called "can JB weld made parts hold up to industry standards" 😀

  38. I'm watching after jb welding my spark plug in my s10 engine used the same product hopefully it works half as well for me as it did for you. If anyone is interested on how this goes let me know I'll update this post till it fails. Good video thanks

  39. Time to use this on a car i see for sale for $500 with a cracked block. I'm on a strict budget, and I'm looking forward to the results as my life would change by trying jb!

  40. The only thing JB weld can't put back together is my marriage and financial stability. Your content is the absolute best. Dare I said you're the most unbiased person to have ever walked the earth. You're awesome!

  41. You said it…..when you put the excess JB weld on….I immediately thought you should have sanded it down ……..But now we see how tough the JB weld held up to the multiple hits from the piston…..Great test"….

  42. I dropped a "performance" 2-stroke ATV motor onto my garage floor once and cracked/knocked a corner out of one of the case halves. I used the standard JB weld to repair/replace the missing corner (broken piece fit into the "hole" cleanly). That case has held up for 2 decades of HARD riding without issue either mechanically or any oil leaking. Another WIN for JB weld.

  43. I have been using jb weld on stuff since i started watching this channel. I fixed a turtle head..(its a cement turtle that holds a table umbrella) I used it to repair my windshield wiper transmission which saved me over a hundred bucks. Ive used it to repair steps on my deck. Its amazing.

  44. Jb weld has saved my butt so many times. I repaired a cam sensor in a 3800 Buick and during hurricane sandy I repaired my awning when it pulled the screws our a cinder block wall.

  45. Talk about "cracked heads"…Start with the left side of the CONgress house and
    don't stop working your way around till all those holes are sealed!!!

  46. There's a German company called Weicon, try testing their products if they are available in the States.
    They have loads of different kinds of bonding agents and other stuff.
    Thanks

  47. I enjoy your videos a lot! I would love to se a video about your background and how you got into youtube. If anyone else agrees like so we can get a background video!

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