Why Hole In Engine Block [Reasons + Solutions]

The main things that can lead to a hole in engine block are a broken connecting rod, lack of oil, and extreme weather conditions. You can tell if you have holes in your engine looking by looking out for some common symptoms.

hole in engine block

These symptoms include oil leaks, coolant leaks, mixing of oil and coolant, smoke from the exhaust, engine overheating, frozen coolant, and low engine compression. Keep reading this article to find out all about them in detail.

We’ll also discuss when it’s possible to repair a cracked engine and whether it’s a good idea to do so. Let’s dive in!

Why Hole In Engine Block [Reasons + Solutions]

It’s never a good sign to find a hole in the engine block. You’ll usually have to spend big bucks to repair it and get back to driving your car.

In most cases, it won’t make any sense to repair the engine block as the costs will be too high. Let’s look at why it happens at first.

What Causes Hole In Engine Block

Not looking after your car properly can lead to holes in the engine look. Here are the most common reasons behind it:

1. Broken Connecting Rod

The connecting rod is an essential component in the engine that connects the piston with the crankshaft. It’s stretched and compressed in every motion when it converts the piston’s linear motion to the crankshaft’s rotational motion to run the car.

broken connecting rod

With time, the connecting rod can wear out and be damaged. When it gets broken, it can go through an engine block and create holes in it. It’s called throwing a rod. Damaged rod bearings can also leave a hole in the oil pan or the engine block as well.

The main thing that people do to damage their connecting rods is over-revving their engines.  At high revolutions, the chances of breaking them increase significantly even if the tachometer hits the red line for a brief moment.

Connecting rods can go bad because of fatigue and years of use. The metal wears out after years of use and finally breaks. It’ll happen faster when there’s a lack of engine oil in your car.

It can also happen due to the failure of the piston pin as it can snap the connecting rod and detach it from the engine. 

Another reason behind damaged connecting rods is hydrolock. It means that water gets into the piston chamber and deforms them. You increase the chances of it happening when you drive in flooded areas or big puddles.

2. Lack Of Oil

More often than not, an engine block hole is the result of a car owner’s negligence. All the components in the engine need to be lubricated to function properly and increase their lifespan.

lack of oil

But if you don’t refill the oil when necessary, it can result in a catastrophic failure like a hole in the engine block.

3. Extreme Weather Conditions

Living in areas that have extreme temperatures can also result in holes in the engine blocks. If you live in a particularly warm area, the engine can often be overheated. It can cause a head gasket or cylinder head to warp and eventually make a hole.

 extreme weather conditions

The situation isn’t much better if you live in an excessively cold climate either. The freezing of the engine block can make it crack. When a coolant is frozen, it expands and pushes the metal around it. It can lead to cracking the engine block and making a hole in it.

What Are The Signs Of Holes In The Engine Block

Sometimes, hole-in-engine block symptoms can be obvious and stare you right in the eye. When the hole is big enough that you can visually see it, you don’t need any further inspection.

But during other times, you’ll have to do a little more work to know if you really have a hole in the block.

The symptoms of a cracked engine will be different based on where the crack has formed and how big it is. With that said, here are the main signs of having an engine block hole in your car:

Oil Leaks

The engine block can crack both on the inside and outside. When it cracks on the outside, you may see puddles of leaking engine oil under your car. Even if you don’t notice any major leaks, check the oil level in your car with a dipstick.

engine oil leaks

If you’ve refilled it recently and it’s lower than what it’s supposed to be, you can confirm that you have an oil leak. The lack of oil could very well throw the connecting rod and lead to a hole in a block of the engine.

Coolant Leaks

Just like oil, the coolant leak in your car when there’s a hole in the engine block. The coolant can go down the side of your engine and it can look like it’s coming from nowhere.

coolant leaks

Any cracks on the outside can cause this issue. Check the level of coolant to see if its level is too low.

Mixing Of Oil And Coolant Leak

When the cracking of the engine block happens on the inside, the oil and coolant can get mixed together. If you notice engine oil on top of the coolant, that’s a sign of a cracked engine block.

mixing of oil and coolant leak

The oil in your car can also look like chocolate milk after getting mixed with the coolant. Be on the lookout for that as well.

Smoke From Exhaust

If the crack is at the top of the engine block, the oil or coolant can get into the cylinder and foul the spark plugs. It can cause a misfire and lead to smoke coming out through the exhaust pipe.

smoke from exhaust

Engine Overheating

Cracks in the engine look are often accompanied by coolant leaks. So, your car can easily get overheated due to the lack or absence of coolant.

engine overheating

The check engine light can turn on indicating that your engine is too hot when it happens.

Frozen Coolant

This is the opposite of the engine overheating issue and it can happen if you live in a cold climate.

frozen coolant

The coolant inside your radiator can get frozen and cause the engine to crack. So, having frozen coolant is a big sign of having a hole in your engine.

Low Engine Compression

Your engine needs to compress a good mixture of air and fuel into a small volume to run your car properly. But when there are holes, the air can leak outside and lead to low compression.

low engine compression

You’ll often experience engine misfires, loss of power, and poor fuel economy when you face this problem.

How To Fix Hole In Engine Block

Fixing an engine block is not an easy task by any means. So, can you fix a hole in the engine block?

It’ll depend on some crucial factors like the size of the hole and how much it has damaged the other components in the engine. In some cases, it’ll be impossible to repair it and your only option would be to replace it.

But the holes that are small can still be repaired if you can find an expert mechanic who knows what he’s doing.

So, how to fix a small hole in the engine block? The mechanic working on your engine will have to completely take it apart at the start.

Yes, you heard that right. All the parts will have to be disassembled and removed from the engine block.

Then, he’ll have to do a pressure test to determine whether it’s strong enough to handle the repair work. In a few cases, the crack can be covered by welding the engine or inserting repair plugs.

What Does It Cost To Repair A Cracked Engine Block

It may seem like good news that it’s possible to repair your cracked engine on a few occasions. But wait till you hear the hole-in engine block repair cost and then you can decide whether it’s a good idea yourself.

Firstly, the chances that your engine will be okay to repair are slim, to begin with. It may not even be an option for you.

But if you can get lucky and find that it’s possible in your case, you’ll be running your bank account dry. It’ll require new bearings, seals, and gaskets to even repair an engine.

The parts needed to cover the hole will easily set you back at least $1500 or more. Let’s not forget the labor costs.

Repairing a cracked engine block can take 10 to 35 hours. So, even with a $50 per hour labor cost, it can go up to an additional $500 to $1750 on top of the price you paid for the parts.

Not to add to the pile of bad news but remember that this is the lowest you’ll have to spend for an engine repair. If there are other damaged components, the costs can go up to a great extent.

Should You Repair A Cracked Engine Block

Now that you know that the costs to repair a cracked engine block can easily rise up, we recommend against it.

Even if you repair it, keep in mind that it’ll now need frequent servicing and that’ll also add up to the costs. It seems like a really bad deal to go through with it.

So, what are your other options? If you want to keep your car, the most suitable option for you is to find a used engine block that matches yours and replace it. Engine block replacement cost can also be expensive but it’ll perform a lot better in the long run.

Unfortunately, it can cost more than the price of your vehicle sometimes, especially, if you can’t find a used engine and need a new one. In that case, selling your car can be a good option.

There are plenty of websites and dealerships that are always open to buying cars in any condition. The fact that you have a damaged engine block wouldn’t throw them off. You can sell it to them if they offer you a fair deal.


Is it okay to drive with a hole in the engine block?

You can drive with a cracked engine block if the damage isn’t too severe but it’ll most likely get overheated soon as the coolant and oil will leak from it.

Can you use JB weld in an engine block?

Using an epoxy such as a JB weld and a sealant on a cracked engine block can prevent air or coolant from being drawn to the crack and leaking out.

How to fix a hole in the aluminum engine block?

A cracked aluminum engine block is easier to repair and weld compared to a cast iron engine block as the former has lower melting points. You won’t likely run into any issues when welding aluminum blocks.

Will a cracked engine have lower power?

There won’t be sufficient combustion pressure when there’s a crack in the engine block and it’ll lead to reduced performance. 


When it comes to car problems, it can’t get much worse than discovering a hole in the engine block when you’re driving it. But now, at least you know how you can confirm if it’s happening to your car by looking for the symptoms and also why the engine gets cracked.

Remember that it’s almost always a better idea to replace the engine block altogether than repair it. But at the end of the day, it’s your decision. Comment below if you have any questions about cracked engine blocks.

About John M

John contributed as a technical head at an automobile company just 2 years after his post-graduation in Automobile Engineering. He loves to lead a free life, so he left his job & started blogging. Now, he does research on every automotive problem, part & product and seeks a better solution & best products & shares his findings with his readers to help them as well as to minimize their struggle.

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