Why is there a hole in the engine block?

What would you do if you detected a hole in your engine block? While this could be a surprising and worrying discovery for you, it’s certainly not something out of the ordinary.

In fact, many cars out there tend to have an unintended hole(s) in the engine block. This often begs the question; what causes it?

Well, several issues can cause that, including; the dramatic expansions and contractions of a frozen engine block, engine block manufacturing defects, and the impact of a malfunctioning connecting rod. Low engine oil levels and broken valve springs are also common culprits of this problem.

The Possible Causes Of this Problem

1. Expansions and Contractions Of an Engine Block

If the car is parked or covered in snow, it’s very easy for the engine block to become frozen, especially if there’s no antifreeze. If you turn the car’s ignition on, the engine may just start normally, going from freezing temperatures below 0° Celsius or 32° F to those above 60–65° Celsius or 140° F – 150° F.

The extreme temperature variation can cause a dramatic expansion of the engine block. The effect of the cooling system trying to pump frozen water around the block to lower the high temperature can cause the block to contract in the same way.

This dramatic expansion and contraction can cause a crack in the block, eventually developing into a hole in it.

2. Engine Block Manufacturing Defects

Engine blocks are often created from either cast aluminum alloy or iron. Of course, each material has its own pros and cons. For instance, the former is much lighter, more heat resistant, and easier to repair.

On the negative side, it’s weaker and cracks more easily. As for the latter, the material is heavier and harder, not to mention that it cracks less easily. Unfortunately, iron has poor heat resistance quality, plus it’s very difficult to repair.

Now, during the casting of the engine block, the block may develop a tiny crack or hole due to a manufacturing error. This can result in an engine block with a small crack or hole that can escalate over time.

3. The Impact of a Malfunctioning Connecting Rod

Also known as “con rod”, the connecting rod that connects the piston to the crankshaft, converting the reciprocating motion of the piston into the rotation of the crankshaft can sometimes fail due to one reason or another.

Notably, a malfunctioning con rod can have a bad impact on your engine. For example, it can break inside the engine block and get propelled through the block, creating a hole in it.

4. Low Engine Oil Levels

In fact, this is one of the biggest culprits for this problem. After all, a hole in the block often means a thrown connecting rod, which is in turn caused by excessive engine RPMs.

These RPMs are normally a direct consequence of driving a car that has an excessively low oil level or no oil level at all.

5. Broken Valve Springs

Valve springs are located around the stem of a valve, which is found within the cylinder head. These springs help protect pistons and cylinder walls among other delicate engine components from compression damage.

They do that by forcing the valves to completely close and secure the proper amount of compression.

Unfortunately, these engine accessories are prone to breaking down. The worst part is that, if broken, the springs can cause the valve to drop into the piston.

Consequently, this can cause the piston together with the con rod to crack and create a hole in the block.

Can an Engine Block With a Hole Be Repaired?

Yes. However, that depends on the size of the hole and the extent of any damage it may have caused.

Can You Seal a Hole In An Engine Block?

Sure, you can. The most common method to do it is welding. Other methods entail inserting a repair plug into the hole to effectively seal it or patching it up with metal glue.

For starters, the repair plug is a sticky, nail-like object that gets inserted into the punctured area of an object and adjusted until the puncture is properly sealed.

How Much Does It Cost To Fix a Hole In An Engine Block?

It can cost an arm and leg to have your holed engine block repaired. This is due to the rigorous nature of the engine block disassembly and assembly processes.

In fact, you can expect to pay anywhere between $1,500 and $4,000, just for a simple repair service. Sometimes you’ll find that replacing a punctured engine block is cheaper than repairing it.

Can You Drive With a Hole In Your Engine?

Though the vehicle won’t have a problem moving, driving with a hole in your engine block is a very dangerous practice. After all, the petrol or diesel, which your car is using could leak into the overheated parts of the engine, causing an explosion. That’s if one of the cylinders is affected by the hole.

Can an Engine Block Be Welded?

The short answer is yes, especially if the block is made from aluminum alloy rather than cast iron. However, this can be a challenging undertaking because of the nature of cast iron.

As said earlier, cast iron has lower heat transfer capabilities than aluminum iron. As such, it can more easily crack compared to aluminum, if welded normally. This can cause further damage to the already damaged engine block.


Lots of cars out there are susceptible to having a holed engine block. This problem is usually caused by a variety of issues. expansions and contractions, engine block manufacturing defects, and a malfunctioning connecting rod are just but a few.

So are low engine oil levels and broken valve springs. Did you know that, in 2021, Chrysler issued a safety recall for their different car models because of a problem that could potentially cause a puncture in the engine blocks of those cars?

These vehicles had faulty engine calibration software that could not warn about low oil volume. As such, the company was concerned that this could lead to those vehicles’ engine blocks developing holes.

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