Top 7 Symptoms for a Cracked Engine Block

Symptoms of Cracked Engine Block

It’s very easy to misplace a bad head gasket for a cracked engine block, and it’s important to know precisely what to suspect when you start noticing some unusual signs in your car. But how do you know your engine block is cracked?

Leaks, engine overheating, contamination in the antifreeze or oil, a mixture of oil and water, low engine compression, and reduction in overall engine performance are some of the most common cracked engine block symptoms.

But as I mentioned earlier, a bad head gasket also mimics some of the cracked engine block signs listed above, which is why you need to consult an expert for a proper diagnosis if you ever notice any of these signs.

Cracked Engine Block Symptoms Video

Top Symptoms

Below are the most common symptoms of a cracked engine block:

1. Visible Crack

The easiest way to figure out if you have a cracked engine block is to look out for visible cracks in your engine block.

You might need to pull out your car’s engine and thoroughly inspect it. You might need an expert to help you with this, but this is your best shot at figuring out what is wrong with your engine block.

Look out for crack points. Are there any visible leaks or fracturing in the engine block casing material? You can make it easier by cleaning the engine block before the inspection.

2. Engine Smoke

Didn’t you notice any visible cracks in your engine block? That doesn’t mean that you don’t have a cracked engine block.

Engine smoke is one of the notable symptoms of a cracked engine block. The smoke will usually come from inside the engine, emanating from any of the cracks.

Engine blocks handle the combustion process of an engine. They are equipped with heat and cold resistant features. When the crack is severely damaged, the combustion process is jeopardized.

This allows smoke to flow freely out of the engine. These smokes are usually combustion air or engine exhaust gases. They are primarily dark or blue-gray.

3. Leaks

You may also notice leaks in your car’s external or internal system. Visual leaks are one of the major symptoms of a cracked engine block. You should detect oil or coolant leaks.

A cracked engine block will have your water jacked, leaking coolant. These leaks can extend to external leaks where you will start seeing oil on the ground. You might see coolant on the floor.

This usually happens if the outer part of the engine block is cracked. You need to understand that a bad head gasket also presents similar symptoms.

The leaks of a cracked engine block happen externally or internally. The internal leaks can lead to coolant leaking into lube oil or lube oil leaking into the coolant. This will result in the contamination of both elements.

4. Oil and Coolant Contamination

Cracked engine blocks are usually posed with problems of oil and coolant contamination. The engine and coolant will end up mixing. You will notice that the coolant will leak and contaminate the oil while the oil leaks through into the antifreeze.

This happens because these elements have found cracks that grant them easy access to other components where they shouldn’t be found.

The engine block contains passageways that independently transport oil and coolant. These passageways will be compromised if the engine block crack is close to the passageways.

In this scenario, you might start noticing milky-colored oil. This is because the antifreeze and oil have mixed. Oil in antifreeze or antifreeze in oil is one of the most common signs of a cracked engine block.

If you have checked for leaks, smoke, and cracks and couldn’t find any, it is high time you checked the state of your oil or antifreeze. You can do this by simply lifting your radiator cap to check the form of the antifreeze or using an engine dipstick to check the state of your oil.

5. Overheated Engine

Engine overheating occurs when there is a crack in your engine block. This can happen because there isn’t proper combustion or because of the coolant and oil contamination.

The antifreeze or engine coolant helps to keep the engine within the required temperature. It protects the engine against overheating or influence by external temperatures. When the antifreeze is compromised, it causes the engine to overheat, which is dangerous for the health of the vehicle.

Sometimes, the “engine over-temperature” light is triggered in this case.

6. Low Engine Compression

For an engine to operate, compression is necessary. Engine compression is the last stage of combustion. It involves pressing together the mixture of air and fuel for power generation.

The engine compression is not static but dynamic – it changes over time to match the load and speed of the engine. When the engine block is cracked, compression is affected. Low compression will only happen if the engine block crack is deep or severe.

7. Poor Engine Performance

The resulting factors of a cracked engine block will affect the engine’s performance. For instance, low engine compression will lead to engine rough running or misfiring. This can go as far as triggering a “check engine” light on your dashboard or a “low coolant level” light.

These engine defects can range from overheating to having combustion gases in the cooling system or even white smoke from the exhaust pipe. When you notice any symptoms, be aware that your engine block might have a crack.

Will An Engine Run With A Cracked Block?

With a cracked block, your engine runs but not as well as you expect.

A cracked engine block will still run but with reduced performance. This is because there are chances that the crack has caused low compression, compromise, and loss of oil and antifreeze.

A cracked engine block sometimes wouldn’t allow you to move the car an inch. The extent of crack and damage will determine. The truth is, we wouldn’t advise any driver to take the risk of trying to drive with a cracked engine block.

It is extremely dangerous to do so, and you might end up causing more damage to the car.

How Long Can You Drive With a Cracked Engine Block?

I wouldn’t want to sound like a bad car instructor, but you can drive for a few miles with a cracked engine block. I will advise against doing this, but the truth is, you can. But don’t do it.

The distance you can drive with a cracked engine block depends on where the crack is located. If the crack leads to the water jacket that connects the engine cylinder, then you might be unable to drive the car.

However, if you still insist on driving a car with a cracked engine block, you should consider removing the radiator cap, eliminating any pressure on the cooling jacket. You can go as far as you can if there is enough water in the radiator.

No matter what or how you try to do it, always remember that driving with a cracked engine block for any length of time will damage the entire engine and put you and those around you at great risk.


We believe you understand the common symptoms of a cracked engine block and can quickly diagnose your car for repairs.

Remember that a bad head gasket is similar to a cracked engine block. It would be best if you considered hiring the services of a professional before making conclusions on your engine block.

Frequently Asked Questions

What does a cracked engine block sound like?

A cracked engine block produces some of the most annoying sounds you might have heard. A cracked engine block can make some grinding sounds.

How much does a cracked engine block cost to fix?

The cost of fixing a cracked engine block usually sits on the high side. The average cracked engine block repair cost runs between $1,000 - $4,500. The repair cost depends on the serviceman handling the repairs, the crack’s location, and the damage done to the cracked engine block.

What happens if my engine block is cracked?

Here are some common things you should expect if you have a cracked engine block: engine overheating, coolant and oil leaks, reduced engine performance, engine smoke, low engine compression, and oil and antifreeze mixing.

Is it worth fixing a cracked engine block?

If you spend a couple of dollars fixing a cracked engine block on an old, weak car, you will have to deal with other costs and expenses. You have to weigh the value of the car with the cost of repairs against simply purchasing a different vehicle.