How to Repair a Cracked Engine Block

Cracked engine blocks can lead to problems such as leaking cooling water so for that reason they need to be repaired. Belzona offers a solution that does not require hot work or specialist tools and is proven to provide a long-lasting alternative to costly replacement.

Materials Used:

How-To Guide:
Step 1: Before starting work on the repair, make sure the damaged area is thoroughly cleaned and free of grease, oil and dirt. We recommend the use of Belzona 9111 and a stiff bristle brush to remove all the surface contaminants.
Step 2: Terminate all cracks by drilling holes along the length of the cracks and at both ends. This helps to prevent crack propagation.
Step 3: Insert studs into holes and using a grinder, cut all the studs flush with the casing.
Step 4: ‘Vee’ out all the cracks with a hand-held machine fitted with a cutting disc and roughen the entire repair area to ensure excellent adhesion of the Belzona repair material.
Step 5: Once again, clean and degrease the repair area and apply masking tape to the area to be repaired.
Step 6: Measure and cut a piece of Belzona 9341 to the size of the masked off repair area.
Step 8: Apply a thin layer of Belzona 1111 to the prepared surfaces pressing firmly with a stiff bristled brush to ensure full contact with the surface.
Step 9: Wet out the Belzona 9341 with the mixed Belzona material and bed it down over the crack into the layer of Belzona already applied using an applicator.
Step 10: Apply another layer of Belzona material to create a buildup of approximately 1/8th inch (3mm) over the entire area.
Step 11: Remove the masking tape and leave the repair to cure. After the product is fully cured, the engine is ready to be put back to service!

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[travisc]

THIS PRODUCT WORKS! I used carb cleaner and starting fluid to clean my surface. I then dipped the bolt in 3 in 1 oil, placed it in the hole. Mixed Belzona per specs, and packed it around the stud and put more than needed. I then smoothed it out with my gloves dipped in carb cleaner. This allowed me to smooth it out nicely. I did this on a 302 block that cracked by the water pump.

[summitcastle]

Research this company. They do amazing things using chemical bonding. I was fortunate enough to have met the owner. Very knowledgeable people. This was invented for military use.

[JalopyTechnology]

Back in the 1970's I drove a Freightliner that had a hole in the block repaired with fibreglass and epoxy... never leaked and the engine ran that way for tens of thousands of miles.

[half_r_mk]

They should have tested the engine run to see how the seal worked.

[TOMBSTONESTAN]

Nice quick vid. This is how I like them, no faffing about and straight to the job. 👍

[lux]

We're going to need 16x the detail

[chemstrsafariks.r.o.]

Really nice video of whole process of renovation.

[shawntincher]

It’s really interesting and educational learning it’s showing you how to fix crack engine take steps on how to where you’ll need drill the holes on where it’s repaired

[YoungHeartedSoul]

Wish you guys sold your product in the USA in smaller quantities. I tried getting in touch with corporate via email several times and no one ever answered my emails. I spoke to a loca belzona distributor but he said the smallest amount sold is quite a lot and all I needed was a small amount to repair a rotted piece of cast iron on an engine water pump outlet. Would be perfect if you sold it in sticks like JB Weld does. I gave up trying to contact you guys and will try welding the area with Muggy weld 77 rods.

[tatewinters]

Very cool. Would 100$ cover the cost of fixing a cracked engine block? Thanks!

[DaytonCarCare]

I think I'd probably just buy a good used replacement motor or block. I once had an Audi TT 1.8t with a failed piston. I just purchased another good used block with pistons from a VW Jetta (same block) for only $150. Swapped the cylinder head and everything else over from the TT engine. Ran great after that.

[bradtodd]

I used this to try to seal one of the infamous "shifted casting" #53 Cummins/Dodge diesel blocks that cracked, and was leaking coolant. I made the weld repair with Muggyweld rods which leaked immediately - contrary to their "testimonials" and the owner's advice! I then prepped and applied this very expensive crap to try to seal any coolant leaks. The Belzona engineer gave me wrong prep instructions (wrong size of sandblasting compound) and the Belzona failed and leaked. Ground all the Belzona off, tried more Muggyweld, then sealed it again with Belzona. Belzona provided 1/2 of the material to re-do the job, and the engineer even came out to watch and instruct. It held for less than a year, then failed again! I control the "leaks" with Fiberlock cooling system sealant and will be replacing the block some time in the future. I read all their glowing testimonials (both Muggyweld and Belzona) that suckered me to spend hundreds and hundreds of dollars on these failed attempts to repair. Save your money - Muggyweld cast iron rods don't work on engine blocks that heat cycle. Belzona is over-priced snake-oil epoxy that cracks and delaminates even with an engineer-supervised application. In addition, I had a new, unused container left over (sealed/never opened). This was very expensive. Went to try it for another (different) kind of project and found it had hardened! Belzona informed me that there is a fairly short shelf life (which is NOT printed anywhere on the container or conspicuously in the instructions!), and since I couldn't locate my original receipt, they would not be replacing the (very obviously new, unopened) container, nor give any kind of credit! Very strange snake-oil company marketing overpriced epoxy!

[shawntincher]

To know what your doing your going to practice lot on learning knowing to do this kind of stuff you gotta pay attention focus on what your doing if your focus listen to your boss they’re not gonna wanna keep at your job it’s very important to pay attention at your job if your really close attention and take advice from other showing how to do it properly

[chlyon]

I heard brazing works well too low heat, may not work in this exact situation but for broken off lugs etc

[spicky]

could you sandblast the area instead to avoid the chemicals...

[dangates]

i had a 79 ford bronco 30 gallon fuel tank. the whole bottom of tank had pin holes on the entire bottom surface when i removed the skid plate it was rotted away from the two metals contacting each other. i ground all the rust and loose debris on the tank, smeared a liberal coating of belzona let sit for 24 hours. people were saying when you put the skid plate back on it will smoosh the plat to the tank, and crack the repair. i was concerned. it never leaked again till i sold the truck years later!

[BrokenLifeCycle]

What's the advantage of this over the tried and true metalock and stitching?

[travisc]

I used this on a broken water jacket on my 302 Ford engine. Hopefully it will work. 🤞

[PAKfromFYCB]

i did not have success with this product and followed this procedure exactly. it was a cat3126 tho so of course the entire corner of the block would have popped off if the head was removed

[bulgingbattery]

If your demolition derby car engine is damaged beyond repair, you can have the engine block melted down into molten metal, and then reforged back into shape.

THIS ENGINE DON'T QUIT!