Cracked Engine Block: Symptoms, Causes and Repair Tips

A cracked engine block is a major issue for any car! There are serious symptoms to look out for and even more serious repair costs! Read on to see how to spot a cracked engine block, what your options are to fix, or decide to sell it to cut your losses. 

5 Cracked Engine Block Symptoms

If you have a cracked engine block, you might not know exactly what’s wrong, but you will definitely be able to tell that something is wrong. Here are 5 cracked engine block symptoms. Many of these symptoms are similar to a blown head gasket, so if you notice any of these, it’s best to get it checked by a mechanic to see if it’s a cracked engine block or head gasket problem. 

Smoke coming from the engine

This is very likely to happen because smoking coming from the engine can occur from two different causes. The first cause is that when there’s a crack in the engine, emissions fumes escape through these cracks. That means the emissions won’t travel through the exhaust system and exit through the muffler, and the gasses will escape through the cracks. 

Another cause of the smoke is when you have a deep crack in the block, motor oil and antifreeze can mix. When oil gets into the antifreeze, it can burn and create foul smells and smoke. However, this smoke is likely to be coming from the exhaust pipe. This smoke will have a blackish-blueish color, so keep an eye out for that. 

Your engine is overheating

When you have a big enough crack, especially in the “right” spot, your coolant and antifreeze mixture will leak out of the block, and the engine will no longer have the capability to cool itself. This is a huge problem because driving with a cracked engine block will cause the overheating to get worse, and it’s likely the overheating will cause the crack to get even bigger. If you see that your engine is overheating, it’s best to get it checked by a trusted mechanic as soon as possible.

Poor engine performance

A cracked engine block means that the seals aren’t effective and will allow some pressure generated in the cylinders to escape. This causes low compression, which means your engine won’t be delivering the regular amount of power to the transmission and the wheels. If you notice a drop in performance from your car (especially with any of these other symptoms), you likely have a cracked engine block. This is actually the most noticeable sign of a cracked engine block, so get your car checked out by a mechanic if you do notice this. 

Oil mixed with coolant or antifreeze

This will often cause smoke that we discussed above, but not always. When you do your regular maintenance on your car (like changing the motor oil or coolant), look inside the fluids to make sure they appear as they should. If you change your coolant and see black specks of liquid floating on top, motor oil has likely seeped into your coolant. 

Or, if you see a milky white liquid in your motor oil, it’s likely that coolant has leaked into the motor oil. Either way, it’s a sign of a cracked engine block and will need to be examined by a mechanic.

You can see a crack in the block

Well, it’s unlikely that you will see the crack because it’s not that easy. The engine will require some disassembly for you to see the block, which means this will have to be done by a mechanic. If you’ve reached the point of taking it to a mechanic and they disassemble the engine, it’s likely you’re already experiencing some symptoms above. But once it’s taken apart, your mechanic will be able to see a crack in the aluminum engine block visibly.

What Causes an Engine Block to Crack

There are a few reasons why an engine block might crack. Let’s discuss some of these cracked engine blocks causes below. 

Faulty casting process during production

This one is pretty unlikely, but it’s still a possibility. This would really only cause a crack in the engine block if it happened with very low mileage on the engine. Some engine blocks are die-cast (basically, molten metal poured into a mold), and then they cool and are removed from the mold. Sometimes air bubbles can enter the mold and cause irregularities in the engine that eventually crack. Again, this is unlikely, especially on older cars, as older cars have been driven without problems for quite some time.

Overheating

This is the most common cause of a cracked engine block. Some parts of the engine block contain very thick layers of metal. Other parts, like the pathways that motor oil or coolant flow through, can be quite thin. When excessive heat is present in these thin parts, it is likely to cause cracks. Because some parts of the engine get hotter than others, if there’s a very hot part of the engine and a less hot part of the engine, this discrepancy in temperature can cause an engine block to crack. 

It’s always best to keep your cooling system in tip-top shape to prevent your engine from overheating.

Extremely cold temperatures

The metal expands and contracts depending on how cold or hot the environment is. Overheating causes it to expand too much, whereas very cold weather makes it contract. But it’s doubtful that it will contract to the point of cracking. 

The actual cracking from cold weather happens for the following reason. Just like we mentioned above, there are thin passageways that motor oil and coolant/antifreeze pass through. If your antifreeze isn’t strong enough (or you’ve put water in it for a temporary fix for an overheating engine), that liquid in those passageways will freeze. Because liquid expands when frozen, and it’s trapped in a tiny passageway with thin metal walls, the expansion of the liquid will put enough pressure on the metal walls to crack them. 

You have a turbocharged or supercharged engine

Most cars that come with a turbocharger or supercharger from the manufacturer are designed with this in mind. But if you’ve added a turbo or supercharger, you may be subjecting your engine to greater pressure than it’s designed to handle. Turbochargers and superchargers force air into the engine to create more horsepower, but this extra pressure inside the engine block will make them more susceptible to cracking. 

What Damage is Caused Driving With a Cracked Engine Block

Driving with a cracked engine block might cost you more in the long run, as it can damage other parts of the car and make the crack even worse! Because a cracked engine block will likely cause fluids (motor oil or coolant or antifreeze) to leak outside of where they’re supposed to be, this means you’ll have liquids dripping around the engine bay. And because the engine bay holds a lot of electrical equipment, these leaking fluids can seep into the electrical equipment and create an electrical short (and, in some cases, an electrical fire!). Continuing to drive with a cracked engine block means there will be more and more fluid leaking, increasing the risk that this will happen to you.

What’s even more likely to happen while driving with a cracked engine block are issues with overheating. Because the coolant/antifreeze will leak, it means your cooling system won’t be as effective as it should be. This means you’re even more likely to experience overheating, which will only make the crack bigger. The other issue with driving with a cracked engine block is that it can lead to a blown head gasket, as well. A cracked engine block and a blown head gasket are two of the most serious issues you can have with an engine. Having one is expensive; having both is going to cost you even more money!

Repair or Replace a Cracked Engine Block: What to do?

Fixing a cracked engine block is neither easy nor cheap. If you’ve discovered that you do indeed have a cracked engine block, you’ll want to look into all options as far as fixing it goes. There are some cheap options, like using a marine sealer or epoxy putty to try to repair it, but this is a temporary fix at best, and is no guarantee that the issues will be fixed. (They will definitely get worse over time!) In many cases, getting an engine block replacement is your only option (or getting the entire engine replaced!). 

How to Repair a Cracked Engine Block

Repairing a cracked engine block can range from the very simple (yet often ineffective) solution like using a sealer all the way up to breaking down the entire engine and making more serious repairs. Some of these more serious repairs could be welding or cold metal stitching. Both of these must be done by highly skilled mechanics that know what they’re doing. That means they will be expensive. And unfortunately, that high price tag doesn’t even guarantee anything. They may not work as well as you hoped and might require another fix in the future.