These Symptoms Might Mean Your Car Has A Cracked Engine Block

As the structural foundation of your internal combustion engine, the engine block is one of your vehicle's most crucial components. Among other things, it provides structural support for internal components like the crankshaft and houses the cylinders, where the pistons move up and down to help generate the power power that moves the vehicle. The engine block also contains galleries that let oil travel through to lubricate moving parts, as well as passage openings for coolant to circulate through and take away the heat from the moving parts. 

Once upon a time, they were often made from cast iron, but these days, most engine blocks have moved to aluminium construction. Both materials function effectively in the face of the tremendous pressure and heat cycles inside the engine. Yet despite being built to last, the engine block is not indestructible, and may incur some damage. Over time, the deck surface where the cylinder head is mounted can warp, the cylinder walls can wear down, and the block itself can crack due to overheating. 

Improper installation of engine components, manufacturing defects, coolant freezes, physical impact, poor maintenance, bad water pumps, clogged radiators, and material fatigue are also common causes of engine block crack. But no matter what the cause may be, you don't usually get a cracked engine block without symptoms pointing to it. 

One way your car reveals a cracked engine block is through fluid leak. As oil and water are circulated in the engine, a cracked engine block can cause leaks to form under the vehicle if cracks are external. Usually, external cracks are easier to identify and can often be easily repaired, but things tend to get a lot more complex and challenging if the block is hurting from the inside. In that case, oil can mix with coolant within the engine, resulting in a milky sludge on the underside of the oil cap.

If this happens, your engine oil becomes contaminated and unable to properly clean and lubricate engine components, which can allow metal-on-metal contact and ultimately cause your engine to seize. Sometimes, coolant can leak through the cracks into the combustion chamber and burn as white smoke, which then appears in the exhaust. Other times, a leak in one or more of the cylinders may allow pressure to escape from the affected cylinders. This leads to low compression and poor combustion, and can result in the engine misfiring or running rough.

Yet another classic red flag is engine overheating. As coolant leaks through the cracks, your coolant level will drop over time, causing the engine to overheat. However, as some of you might well know, many of these symptoms aren't unique to a cracked engine block and can also be attributed to a failing cylinder head or blown head gasket. Hence, experts will often inspect and use methods such as Wet Magnaflux testing, pressure testing, or imaging to make sure you're actually dealing with a cracked engine block. 

The average cracked engine block repair typically costs anywhere from around $500 to well over $3,000, including labor costs. Pricing often depends on the size and location of the crack, the repair method needed, and whether there's additional damage. Simpler services such as repairs of tiny cracks which do not require full engine removal and can be sealed from the inside out using sealing agents generally sit at the lower end of the scale.

However, if the damage is more severe and requires welding and machining, or even a full engine rebuild, mechanics will have to remove the engine, take it apart and work on the block before reassembling and reinstalling it. In such cases, it's more likely that you'll see far higher figures.

Should your mechanic spot an issue with internal parts like pistons, bearings, or seals, those parts would most likely need replacing, too, which would drive up the cost of engine block repair. Although in more severe cases, full replacement is often the best course of action, especially if the block's structural integrity has been compromised by oil and coolant contamination. 

A full engine block replacement can set you back between $4,000 and over $8,000. If the cost of fixing or replacing the engine block exceeds or is more than half the current market value of the car, it wouldn't make financial sense to undertake the repair and choosing to junk the car would be the most cost-effective option long-term.