A cracked engine block is bad news—in the world of automotive repair, it’s one of the most serious (and costly) problems you might encounter. Sometimes, the issue is mistaken for a blown head gasket or cracked cylinder head because it can present many of the same symptoms. But unfortunately, a cracked block is far worse than either of those problems, as it usually means your car needs a new engine.
Your car’s engine block is an aluminum or cast iron casting that acts as the bottom portion of the engine. The block provides a foundation for the cylinder head(s) and other major engine components. Also, the block houses the crankshaft, pistons, connecting rods, and (in some cases) the camshaft.
The block and its internal components are often referred to as the “bottom end” of the engine. Meanwhile, the cylinder head(s) and related parts are considered to be the “top end” of the engine.
A cracked engine block is rather uncommon. Usually, the cylinder head(s) crack and start causing problems long before the block does. Still, there are instances where a block can crack, resulting in one or more of the following symptoms.
Note: Because other problems can present the same symptoms as a cracked block, you’ll want to perform a thorough diagnosis of the vehicle before performing any repairs.
There are coolant passages that run through the engine block. A crack in the block can allow coolant from those passages to leak into one of the engine’s cylinders, where the coolant is then burned during the combustion process.
As a result, you’ll see white smoke, which is actually steam, coming out of the vehicle’s tailpipe. You might also notice that the exhaust fumes have a sweet smell.
A cracked engine block can result in an internal or external coolant leak. An external engine oil leak is also possible, depending on the location of the crack.
A cracked engine block can result in a coolant leak (either internal or external) that prevents the coolant from properly circulating through the engine. The engine can start to overheat as a result.
In some cases, a cracked engine block can result in a loss of compression that causes the engine to run rough and misfire.
A cracked engine block can allow combustion gases to enter the cooling system. As a result, you might see an excessive amount of bubbles in the coolant before it begins to boil. You might also notice that the cooling system is under extreme pressure.
It’s possible for a crack to develop between the block’s oil and coolant passages, resulting in coolant-oil intermix.
A cracked block can trigger the check engine light, low coolant level light, and the engine over-temperature light. If your car is equipped with a temperature gauge, you’ll also see it begin to climb.
Engine overheating is the most common cause of a cracked block. When the engine gets too hot, the block can crack as a result of thermal stress.
Also, the block can crack in freezing temperatures if the cooling system is filled with too much water and not enough antifreeze. As the water freezes and expands, it causes the block to crack.
Casting and design flaws can lead to a cracked engine block, as well. For example, eighth-generation Honda Civics (model years 2006-2009) are known for having a casting flaw that eventually causes the block to crack. Honda issued an extended warranty to address the issue.
There are various ways you (or your mechanic) can check for a cracked engine block. Which test method you choose will depend on whether you’re checking the block for an internal or external crack. The most common diagnostic procedures include the following:
In some cases, you can spot a crack that’s leaking oil or coolant externally by performing a simple visual inspection of the block.
Usually, a block with an external coolant leak can be diagnosed by performing a cooling system pressure test. The method involves pressurizing the cooling system (with a dedicated pressure tester) to pinpoint the source of the coolant leak.
The video below demonstrates cooling system pressure testing:
A cooling system pressure tester can also be used (along with a borescope) to check for internal coolant leaks. The process involves first removing the spark plug from the suspect cylinder, then inserting the borescope into the spark plug hole. Finally, the cooling system is pressurized, and the borescope is used to check for coolant leaking into the cylinder.
Coolant leaking into the cylinder can point to a faulty head gasket, a cracked cylinder head, or a cracked engine block. The engine will need to be disassembled to determine the root cause of the problem.
Once the engine is apart, a machine shop can check the block for cracks using fluorescent dye and/or magnetic crack detection equipment.
A block tester—a device that contains fluid that changes color in the presence of combustion gases—can be used to detect a block that’s cracked internally. The tester is placed over the cooling system filler neck to check for the presence of combustion gases in the cooling system.
If combustion gases are present, the engine is suffering from a leaking head gasket, cracked cylinder head, or cracked engine block. The engine will need to be disassembled to determine the root cause of the problem.
The video below demonstrates using a block tester:
In the past, auto repair shops would occasionally fix a cracked cast-iron block via welding, gluing, or pinning. But these days, most professionals will opt to replace the block (or the entire engine) instead of repairing it.
Replacing an engine block (or the entire engine) is a costly and labor-intensive repair. If you choose to have a professional do the job, you can usually expect to pay somewhere between $4,000 and $8,000. Of course, the exact cost will depend on various factors, such as the year, make, and model of your vehicle.
Don’t let your vehicle hang out in the garage for days because of a damaged engine block. If you’re having trouble finding the perfect replacement at local auto parts stores or just want to skip the hassle of scouring shops, shopping online at CarParts.com is a great option.
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Any information provided on this Website is for informational purposes only and is not intended to replace consultation with a professional mechanic. The accuracy and timeliness of the information may change from the time of publication.
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Ok so example block is equipped with what I would hope to be very magnetic material Then heads are nothing more than electromagnetic cylinder caps with each one having its own coil much like todays EFI engines *. Note. Lol. Now changing the programming of the firing time and equipping pistons with a non conductive material And very open air drafting system for less resistance on Motors * strokes. Lol. Now what we have is a 4 -6-8 cylinder electric motor*. With probably no need for coolant or much oil since a person could use air from the displacement of motors stroke to feed into modified bearing or seals which would require only a little compressor oil and wala. Electric motor from a internal combustion engine Cracked block or not. And great gas mileage. Wouldn’t you say.
hi,
i have a 2016 Toyota Dyna/Hino Diesel engine, it has overheating problem and my top gasket was replaced few days ago. now i discovered my reservoir overflow once a crank the engine and my coolant split out
What could be the problem.
Hello,
If the cooling system is under excessive pressure, that indicates combustion gases are likely entering the cooling system from a leaking head gasket, cracked head, or cracked block.
I had a cracked block and I am telling you use kseal. It's amazing. Look it up online. I did alot if reading and was very hesitant to use it but the steam stopped and my engine ran smoother within 30 mins. Please just read about it. It saved my 2001 Ford from death.