Everything You Need to Know About a Cracked Engine Block

Everything You Need to Know About a Cracked Engine Block

Three words that no car owner wants to hear – cracked engine block. Most people think that this means their car is a total goner. Images of huge repair bills begin flashing in their mind. To help ease those fears, let’s take a closer look at what a cracked engine block is, what it actually means for you and what you can do to help minimize your repair bill.

Engine Block Basics

Engine blocks are not supposed to crack. They are built with the intention of lasting for the lifetime of the vehicle; however, sometimes things happen that do cause problems with them. Having a basic understanding of how your engine works really helps you understand what may cause a crack in your block.


Your engine block is where the cylinders are located. They are like large metal sleeves where the pistons move up and down inside them. As the pistons move up and down from small explosions caused by the spark plugs igniting the fuel, they turn the crankshaft. The turning crankshaft transfers this power through the transmission and to your wheels, causing them to turn and your car to move.


Obviously, this is an extremely oversimplified version of how your car operates, but it gives you an idea of what is taking place inside your engine. Now add in the fact that your engine block also has oil and coolant inside, helping to keep those internal moving parts lubricated and cooled. Those two fluids move in separate areas inside the engine, and they should never mix together in a properly working engine block.

What Causes an Engine Block to Crack?

Engine block cracks can be caused by different things, but the main culprit is overheating. Engine blocks are usually made from cast iron or aluminium. Some parts are very thick and others are thin as there are numerous channels running inside the block for fluid movement. As the engine heats up and then cools down, the block can actually expand and then shrink back down. At normal temperatures, this doesn’t cause an issue.


However, when the engine overheats, this expansion can cause big problems. The thinner parts of the block walls expand too far, causing small cracks to develop. Once these cracks develop, continued overheating causes the block to become even more brittle, thus allowing these tiny cracks to turn into real problems.


Another thing that can cause a cracked engine block is extremely cold temperatures. If your car does not have the proper level of antifreeze, the passages inside your block can freeze during very cold weather. Especially if you are using water in your engine as coolant, this water can freeze and cause cracks in the passages of your engine block. This is why it is extremely important to make sure your car has the proper amount and type of antifreeze in it during cold weather.


Excessive stress inside your block can also lead to a crack and failure of your engine. This is usually caused by aftermarket performance parts such as turbos or superchargers. These devices cause the pressure inside the cylinders to be much higher than what the engine block was designed to handle. This excess stress inside the cylinders can lead to a catastrophic failure of the engine block. If you are looking for extra performance, make sure your block can handle what you are throwing at it!

How to Repair a Cracked Engine Block

Just because you have a crack in your engine block does not mean that all is lost. If your engine block is cracked, there are ways to repair it. However, you need to understand that they don’t always work and can sometimes be quite expensive. Here are some of the most common ways to repair a cracked block.


Traditional Welding

Re-welding a cracked block is one of the most common methods for repair. An experienced mechanic may be able to weld the crack back together, essentially filling the crack with new metal. Depending on where the crack is located, the engine may not have to be removed to attempt this repair. Note that if the welding is not done properly, it could cause other issues with your block.


Cold Metal Stitching / Patching

Cold metal stitching is one of the most time consuming methods to repair a cracked engine block. This is similar to stitching fabric together, and it is very susceptible to heat and future cracking. Cold metal patching is a better option, but it is not always successful either.


Block Sealants

These are special sealants that can be applied to the crack that harden into finished products that are nearly as hard as the original metal. These can sometimes be successful, and they are easy to apply as you simply put them into the coolant system and let them circulate through the engine block. This solution will only work on very small cracks.

What To Do If You Have a Cracked Engine Block

Stop driving immediately! Continuing to drive with a cracked block can lead to further damage and an even higher repair bill. With mechanics charging anywhere from $50 – $150 per hour and this repair sometimes taking as much as 30 hours, you do not want to add even more damage to the problem! Continued driving can lead to a blown head gasket, damaged cylinders, and damaged heads. Not good times!


Have a mechanic assess the damage to your engine block. If it’s an easy fix, then it might be worth keeping the vehicle and performing the repair. If the damage is extensive, then your best bet might be getting rid of the vehicle and purchasing something new.


There are car buying services out there like Auto Wranglers who will buy your vehicle for cash regardless of its condition. Plus, they serve hundreds of cities across the country. Don’t even worry about breaking the bank on that repair. Instead, put some money in your pocket and use that to buy a new vehicle that is free of defects.


Bryce Newell is an automotive enthusiast who loves to write about the latest news, products, and DIY projects. While Bryce is an amateur in the field, he is passionate about cars and has been since he spent weekends in the garage helping his dad rebuild a 68 Dodge Charger as a kid.

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