Cracked Engine Block - Will JB Weld Fix It? 

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I used JB to repair my crankshaft on my 350 chevy it held fine even though i'm running 100 shot nitrous. I also used it to repair my wheel hub ,I did that 10 years ago and I run over 150 mph works great. I also blew out a clutch on my work van but made a clutch out of jb weld. I couldn't afford to fill my daughters tooth cavity so i used Jb weld Jb weld is life , i got back with my wife because of jb weld I haven't seen my son in 5 years

My JB Weld story: It was early 80's and I had a Saab 99, which preceded the 900. The harmonic balancer broke off in the winter, here in Alaska, and it was a nice clean break. The break in the balancer indexed very well to the end of the crankshaft, so it was a very good alignment, so I spread on the JB Weld, propped it up to hold it solid and put an electric heater on it all night. I drove that car for over a year before I sold it, and never had a problem.

Most boats’ cooling system are not a closed system so it doesn’t build up pressure like a sealed cooling system with a radiator or heat exchanger so JB Weld will work just fine.

I repaired a Cummins ISM cracked block with JBW behind the engine starter on driver side That was 4 years 215k miles ago and the engine still running strong without leaks. Awesome product. I strongly recommend it.

This stuff, in my opinion works great even as a permanent repair. I have used to repair counter bores on diesel engines, intake manifolds and such. Wonderful product! Very nice job cleaning the area Donnie, you will never have any more problems with that crack due to JB weld failing!

I have a1990 Dodge Dakota 4 x 4 that I have converted into a tractor, it sees hard service. I didn't winterize properly either and ended up with a two in crack just under the exhaust, I cleaned it up and cut a groove in the crack..BUT, the difference in the way I made my repair was that, I applied a VACUUM to the engine VIA the overflow "TIT" on the radiator. I let it pump for about an hour, then I applied the JB WELD, let it keep pumping for another 20 minutes, it pulled it right in, I think that enough JB wasa pulled in to equal the block thickness . I have sice tried this method on several other engines including Marine Engines. It works great, all you need is access to an AC Vacuum compressor. This way the JB is pulled intto the block and not just "stuck" on the outside like a "patch"..and this method works with other Mediums besides JB WELD. Regards , Boyd E. Falk

My father-in-law JB WELDED an engine block on a tractor,it was cracked all the way down the side,it has held now for over 25 years now.If I remember correctly,he put it on in layers letting it dry in between each layer.

I am doing the exact same repair on my 86' 305 Mercrusier. Thanks for the great video!

Had a ford ranger with a cracked block.... ran 57,000 more miles after applying it. It held up and trust JB weld. Now, not all cracks are the same and other cracks in different areas will be different. My crack was at the driver side above the manifold right over the number 1 exhaust port. We also drilled and bottom tapped two holes and placed a steel plank to help with expansion. I know that was probably 95% of the fix, but the JB weld held it all together. It works.... just not with a piston hanging out of the engine lol

I just complete engine, and aftrr two coats of jbweld it holds good on crack when tested at home.So am taking it to a lake for little longer run and see how it will doo.. thanks for the video

I have used JB Weld on the cracked alloy sump on my VW: has lasted 8 years so far and 100,000 miles. Otherwise it would have been an engine/gearbox removal to get the sump removed for welding. Only thing is that the surfaces must be 100% clean and roughened.

Thanks Donnie! great video, I'm getting it right now to put it on a small engine crack on my Goldwing.🤞🏾Take care!!!

Its all in the prep. Clean clean clean! I used it on magnesium motorcycle cases after I threw a chain. It lasted 10 yrs on a motocross bike ridden hard.

Was very skeptical. Recently I was challenged with the same issue. Crack was horizontal with the cylinder head and about 9 inches long. No water in the oil, ran like a top. Opened up my crack a tad more with a dremel, stop drilled the ends with a #30 bit, cleaned the area with a cup wire brush on a 4" grinder and wiped the area down several times with acetone. I applied one coat with a putty knife pushing it into the crack. Waited 6 hours and applied another coat over the area. To my surprise, it worked like a charm with no leaking whatsoever. I'm currently looking for a replacement engine as I'm not sure I trust it just yet but, it did the trick. Thanks for the video.

A good friend of mine used JB Weld on the block of a Ski Natique boat and I've never heard any complaints from him about it since. He finished using the boat that summer and then sold the boat.

Hi Jimmy, I hope it holds out for the summer too....if not, my boys are going to be sad....lol Most of the wheels came with the kit I bought. I had to get the 90 degree attachment separate. This was my first time to use one, bit without air tools, it performed well. Thanks for watching! Oh, in case you're wondering, I found this tool and attachment at Sutherlands Lumber Store!

I hustled wanted to say thanks for posting! I did the same thing after watching this video and it worked. Because of the video I also found the upper leak also and was able to get that one also. Any updates as of late?

Thanks for the video. I forgot to winterize mine last winter. And today is 90f outside and am doing block repair with jbweld. I folow your work and i hope it will work. Exept i had another crack right under manifold so i had to take if off so i could repair crack. I hope it will work after i do another coat of jbweld.

I have repaired a couple of 400 sbc race blocks with JB Weld and it worked very good. The engines had about 650 hp N/A and 300 hp of spray on them. They lasted for a few years each before a different issue put them out of commission.

I'm dating myself, but in the 60's and early 70's Ford sold a metallic epoxy that was very much like JB Weld for dealing with porous castings like engine blocks and cylinder heads (external coolant leaks mostly). Ford never advocated patching cracked castings with it, but there were instructions on using the epoxy properly in the factory service manuals. Improvements in casting technology have pretty much eliminated the need for things like this. Nice test. I'm not a huge JB Weld fan, but I'm glad it's working for you.

I did it on my sear ray 2002 Sundancer. Cranck block, it worked!

I used this stuff today for the first . I thought yeah right big claims etc . But it is really strong , I have no doubt it would hold up on an engine block . And it sticks ,there's no way you would get it off without grinding

I fixed mine drilled out both ends of crack worked for years sold. BOat still running great

Great! Found the vid, as I'd stumbled on the other one, the follow up vid... Gonna fix the crack in the cast iron oil pan in the 7740 Ford tractor... using JB Weld!

AWESOME !!!! My son just recently busted his new RC Truck he got for X-mas :( But thank God, all the parts are replaceable !!! The Pieces he busted need to be able to handle a bit of torque & strength !!! After seeing your Vid & others, I have no doubt that JB Weld will do the trick till his new parts come!! & if the hold up, I may just leave the fixed parts on till needed !!! Thanks 4 Sharing Your Experience Using JB Weld !!!

Trying to do o2 sensor bungs and I was curious if jb weld will be strong enough to mount the o2 senor bung to the pipe?

When I worked for General Motors as a tech. in the transmission shop, we would often have a cracked governor case and GM had a weld that we used and it really worked good. it was grey and took 24 hours to dry. it would hold trans. fluid and heat and pressure. It was also drillable and could be threaded if needed. Just in case that fails you have another option.

Donnie thanks for this video. Bought a Bayliner in Wichita Kansas last summer and only had time to use it once. Then when I took it in for winterization this fall. The mechanic told me that because there were new freeze plugs installed, I probably bought a boat with a cracked motor. This statement was given by assumption, not by visual. Can't wait for it to warm up to check. And if crack is found, try your technique. Hopefully it will not be cracked. But if it is, this could save me the cost of a new 454 Mercrusier. Wish me luck. Will post results.

Thanks for sharing mate!

Hey Donnie, Great video-did all the drill bits and grinding wheels come with the 90 degree Dremel attachment? I hope the repair holds out for your summer on the lake.

Back in 1986 my dad let his tractor freeze up. an old a/c it cracked the block on the side about four inches long I cleaned it up real good an ground a little right in the crack.i cut a little line at each end of the crack an filled it in with jb weld it never leaked again an he drove it another 20 years still holding when he sold it in the auction. Trust me I'm a believer just take the time to do a good job on the prep work an it will hold it's amazing.

That engine is more shaky than my grandpa lol 😂

did same to mine works great

I had a casting defect on a cylinder wall on an old ford tractor that i repaired with jb weld. it was a pinhole, and i was able to get to it from the backside. havent had any problems

I've a tiny oil leak which I think I've found where AC compressor is bolted to crankcase . Just changed my oil and filter . I'll make sure before trying anything . Tiny since I think it goes down very slowly just annoying . Yeah I hit something very hard . Possibly a problem if it still leaking when I try using permex / JB weld grey or black glue since it's supposed to be clean and dry ? Any helpful experiences out there ? Do I have to wait till I drain it during my next oil change ?

Hei Donnie, I have a similar crack on my car's disel engine (150 hp). The crack is smaller than that and is on the coolant side. Do you think it will do the job? Thanks for the detailed video.

it stil leaks, i see the water drops in the video, is that taken after testride or? or when u discovered that new leak?

hi donnie, my name is mark and i watched your jb weld video out of interest. nice looking job. the video shots looked like falls lake, north of raleigh, nc. just wondering if it was. good work. mark

Hi Donnie my brother and I just fixed our truck motor with jbw we hope it's going to be all good thanks

I tried using JB weld on a CAdillac Engine to seal a crack. I ever poured it insode of the water jacket to seal it from inside and then also applied it on the outside. As soon as the engine got hot the JB weld cracked and started leaking. ALso i did all the preparations necessary for JB weld to stick well to the surface.

is it leaking from the heat exchanger?

Good job

I am gonna have to do this on my boat as well, my only concern is hoping it did not crack inward as well.

Hi, what was leaking from the crack? coolant or oil? if oil please let me know if it's pressurized area or just under crankcase pressure? thank you for the tip, gonna try this and hope this gives me a few months until i replace my engine

How long did it end up holding up for

Anyone have an update on how long this held? Looks like after our killer winter in Texas I’m gonna be trying this.

Wow...that is good to know! Maybe mine will last a few years. If it works on a 650 hp, than I should not have a problem. Thanks for letting us know about this!

Any concern about the JB Weld getting inside via the crack? I need to repair an OB gearcase, don't want to get any of it onto the gears themselves.

Regular jb weld or the blue tube marine jb weld???

Hi, from Argentina, I have a Mercury 135Hp 2-stroke with a crack in the block.I want to try fix it with this product. You made it un 2013, how is now de engine?.-

My 350 sbc block cracked below exhaust about to fix mine the new k&w lime green bottle to run through coolant works great but I'm not big on mixtures in my motor good luck

I have read a lot of articles about this as I too have a cracked block on my boat. A lot of nay sayer's, but you know what? Not one person has stated they have done it and thus had any ill effects. Only people who advise against it and recommend replacing the block. My question is why not try this if your engine is fucked your engine is fucked, right? I could see if you were going to take ur boat 50 miles out to sea. But for lake users... why not? Again, not one person saying that they used JB weld and it turned into a catastrophy. I did my boat today. I will report on how well it worked after I start it up tomorrow evening.

Would this work on a cast iron intake manifold? And should I drill the ends of the crack to prevent it from spreading?

Was that El Dorado lake you were skiing at?

The guy attaching the hose to the water ears ;)

J B Weld repair on K13 nissan diesel block, Extensive prep, laminated several layers. used 4 tubes. Failed

Can JB Weld used to fix a scored piston skirt ?

So its partially drilled right? Not all the way?

Did it last more than just 3 times out ?

Is that a matchbook putty knife? That's awesome. I always have a hard time coming up with something disposable to both stir and apply. I just saw another video that recommended a disposable snap-off razor. Thanks for posting!

I had a cracked block on my tsx tried JB weld lasted about one hour tried belzone 111 the best stuff out there did not work replaced the engine ooouch! if the crack is under pressure(oil) it will not work as it was in my case.

How’s it holding up

Curious to know if it's still holding. If you ever have that issue again try marine tex. I have a back up race motor that ran 2 seasons with a huge patched crack. I'm about to do it again and run that motor the rest of this race season as well. I assume it works great it held up to the abuse of racing.

Is that Milford Lake?

with my mower the reason it has a small crack my engine mount vibrated loose, maybe check your they do vibrate alot

How did this hold up?

86 people saw this a failure , seriously is it permanent>?

milky oil before and after repair?

is it still holding?

@6:50 so he used 2 coats of the JB Weld. Are you supposed to do this?

I had a friend that had a rod knocking in his car and it had done ate up the crankshaft so he took the quick steel epoxy and put it under the new bearing and torqued the crankshaft back down and it has been like that for over a year , I have tried jb weld before on stuff doesn't hold we'll under pressure if I were anyone fixing cracks on the blocks I would remove and leave out the thermostats that way it will never run much over a 100 degrees , and try the quick steel !

I'd use steel wool or powdered iron with jb weld depending on hole size .

when your engine block cracked there was it also putting water into your oil and in your pistons? cause mine is cracked around the exhaust manifold and i had milky oil and water on top of my pistons need to know how serious mine may be i know a technique on welding cast iron properly but before i go into welding it and sealing it i wonder if mine has a more serious crack than it appears

How can I purchase it from where

i like the metal in the backround

How long was the crack would you say? Awesome video and thanks for sharing!

How can I figure out where my engine is cracked if I can't see it but it's leaking oil??

was water actually leaking out of this crack?

sodium silicate is the best thing to use run it for a day or two and it will seal the crack flush and fill and forget the crack

Just had this happen to me bought a boat this way and now I have it cleaned taking it to a welder if he can't do this job it jb weld time still running strong I assume?

yea you shouldn't have any issues out of it. thats how i fixed the 283 csb in my truck and it has held up for 10 years

The manifold in my 96 Honda Civic has a 3 inch crack. I won't be able to replace it for at least 30 days. Would JB weld work?

Just bought a 1997 bayliner 1950 Capri with a mercruiser 3.0 with a crack in exactly the same spot. How did this hold up for you?

I broke a piece of my engine block off on my 2001 Audi A6 and was wondering if jb weld could somehow fix it. It's a more severe than just a crack but I feel like it could work

I worked as a aircraft mechanic, and we had a plane with broken off propellers and guess what? We JB welded those bitches right up and worked like a charm

This stuff is AWESOME!!! Just dont trust the QUICK drying version. Isn't worth a damn. I've used JB weld on LOTS of stuff. Including... gluing a radiator back together on an Acura Integra that overheated and busted. The JB weld held so great.... the car overheated again weeks later.... but the radiator busted in a totally DIFFERENT spot. The JB weld held while radiator overheated with extreme pressure that time!!! Crazy stuff for sure!!!!

No, it is El Dorado Lake!

How long did the epoxy stay on your fingers? Uh... gloves?

Just pulled the boat out and saw the EXACT same crack....I knew I forgot to do something last fall.

Wish I could have used J.B. weld when I cracked the block in my Mark Twain but a valve stuck open and the piston hit it and it cracked the block like a broken watermelon . The valve was the size of a half dollar and it was stuck half way into the top of the piston . The mechanic that replaced the block said he was keeping it cause he was only charging me a little over a thousand to replace the block and it was the worst cracked block he had ever seen and the piston was going on his desk as a paperweight . Never buy a boat with closed cooling if you can avoid it .

Hey, Its been three years since you posted this video. Hows it holding up? We all want to know.

Jb weld will repair ANYTHiNG if you use excellent preparation. It's weakness is vibration but on large rigid surfaces or on small broken parts it will last beyond the years you sell the vehicle/boat.

plus i work on motors i put j.b.on the part to be fixed not the paper.

That makes me confident...i'll try it on my 18 hp lawnmower engine...finding a new engine absolutely sucks since it seems that there not many of them out there in the www...its funny ...every fucking may either my car lets me down or something else that i need every day..my stuff hates me

Is it still holding? And was that an aluminum block?

funny to see the same crack as my boat lol How long has it lasted?

hay Guys nice Job. By the way Quik Steel come in a 500 F Degrees / + 260 C : And 90 F / - 68 C degrees . I just Got Some Today I Plan on Fixing A hole in my Motorcycle Crank Case about the size of my thumbprint . wish me luck :>)

With the motor being enclosed, it was a very tight fit and a spreader may have been too big. You could cut a plastic spreader, which would have been better, but I forgot to pick one up and I did not have one there. Thanks for watching!

thats what happens when you dont winterize your engine