A Hole in Engine Block – Reasons, Symptoms & Solutions

Have you driven your car for years -yet never known the role of an engine block? You are seriously missing out on an extremely important lesson.

It wouldn’t be an exaggeration to put engine blocks on par with a human’s heart or brain; the entire system will collapse without their proper functions!

Hence, a hole in engine block is not something to ignore; you must get down to it to protect your car from further damage. Keep scrolling through Bryan’s expert guide for more!

An Overview of Engine Block

hole in engine block
Engine Block

What Is It? 

Engine blocks (commonly referred to as “cylinder blocks” by some experts) are the casing for all major components that formulate the motor’s bottom end.

These blocks push the crankshaft to spin and make other pistons move back and forth across the bores, powering them up via fuel combustion.

For some car models, the engine blocks are where camshafts are installed, too.

What Are Its Materials?

Usually composed of aluminum alloy or cast iron, the block’s metal construction provides ample strength and transmission ability.

As a result, it can transfer the heat from combustion procedures to integral cooling systems with relative ease.

Even better, the aluminum engine block often incorporates iron sleeves that serve as piston bores. Sometimes, these iron sleeves are substituted for hard plating build-in after machining.

What Are Its Main Features?

In the simplest term, an engine block is a simple metal shape that houses water-cooling jackets, cylinder bores, crankcases, and oil passages.

The jacket contains empty passage systems that circulate the block’s coolant. It also wraps around the cylinders (usually four to eight) and cases the pistons.

How Does It Work?

As the cylinder heads are securely placed on top of the block, the pistons slide back and forth in the cylinders to turn the camshafts over, pushing the wheels.

Meanwhile, the oil pans (at the block’s base) provide a huge oil reservoir, where your oil pump pulls from to supply energy to each oil passage.

That’s how your automobile gets sufficient energy to traverse across the street.

Does Every Automobile Have An Engine Block? 

No. Air-cooled engine motors (such as the Porsche 911 or VW flat) don’t have any engine block.

Their crankshafts – bolted together – just spin inside the engine cases. A bunch of cylinder “jugs” are tightened to them, moving the pistons left and right.

What Causes A Hole in Engine Block?


Broken rods, weather conditions, manufacturing defects, and oil shortages all contribute to tiny holes littering your engine bay.

Whatever the cause, engine overheating and poor performance are on the horizon.

Broken Connecting Rods

The connecting rods are a critical engine component that binds the crankshaft and piston together.

They are compressed and stretched in every movement, converting the piston motion to crankshaft rotation to give your car its operational power.

Sadly, these rods can deteriorate and get damaged. Once broken down, they will slide through the block and leave multiple holes behind (a phenomenon called “throwing rods”.)

Worse, the malfunctioning rod bearings might even create holes in your oil pans! 

So, are there any reasons behind a rod’s worsened condition?

The first thing to look for is over-revving engines. High revolutions increase the risks of broken roads – even if your tachometer only touches the red lines in one second!

Another potential culprit is fatigue and long-time usage. Despite regular maintenance, the rod metal can still wear out and eventually break.

You should not skip the possibility of a catastrophic failure in the piston pins, either; the pins may snap your rods and detach them from the block.

And some experts also put broken rods down to hydro lock – where the water infiltrates your piston chamber and deforms them.

Ask yourself whether your car has been subjected to big puddles and flooded areas lately! 

Extreme Climates and Weather Conditions

Areas/ neighborhoods with frequent temperature extremes also result in engine block holes.

More specifically, hot temp overheats the engine, warping the cylinder head/head gasket and creating holes.

Some cars install a cooling system that pumps frozen water in the engine block to reduce high temperatures – but too bad, it doesn’t make anything better.

The engine block will just keep contracting and break down eventually.

Meanwhile, chilling climates cause both the block and the coolant to crack and freeze.

As a result, the frozen coolant will push and expand the surrounding metal, producing hundreds of tiny holes and ruptures! These holes will grow even worse if your car has no antifreeze solution.

And if all of this weren’t horrifying enough, engine expansions and contractions are not easy to detect.

As you turn on the car, its engine will start normally; most people only realize something’s wrong when it’s too late.

Manufacturing Defects in The Engine Blocks 

As previously mentioned, engine blocks often contain iron or aluminum alloy, both of which have their fair share of upsides and drawbacks.

For one, alloys have great heat resistance, low weight, and easy removal/repair. But on the downside, it’s weak and cracks in a blink.

How about iron? It’s harder, heavier, and much less prone to cracking. Too bad, its heat resistance is below standard, and repairing iron is also quite a pain. 

So whether you choose iron or alloy blocks, risks of manufacturing errors are always lurking on the horizon, resulting in small holes or cracks that might grow bigger over time.

Oil Shortage

In most cases, block holes stem directly from your negligence. How so?

Every engine component must receive enough lubrication in order to work properly and extend its lifespan. Failure to refill your car oil on time makes them run rough, and holes will inevitably pop up! 

What Are The Symptoms of A Hole in Engine? 

cracked block repair
The Symptoms of A Engine Hole

Keep your eye on the following engine block symptoms: 

Oil Leakage

Cracks might occur on both sides (outside and inside) of the block. As its external shell is broken, you can see oil puddles pooling under the vehicle or on the exhaust manifolds.

And what if there seems to be no leak? To make sure, you can check the car’s oil level using dipsticks.

Is it lower than you expected – even though you have refilled the tank recently? Then it’s clear: oil leakages are clearly at play!

As explained above, oil leakage may throw off your rod, leading to holes and crevices.

Coolant Leakage

Like car oil, coolants might also leak if the block suffers from big holes. The liquid will trickle down the engine’s side, looking as if it had come from nowhere! 

Such issues can stem from any external crack; confirm the leak by checking your coolant. Too-low levels are a clear enough signal!

Coolant and Oil Mixing Together

When the cracks occur inside the block, your coolant and oil may get out of their designated slot and mix in together.

So look closer: do you spot any oil on the coolant’s surface? Or does the car liquid look like fresh chocolate milk? “Yes” to one or both questions implies cracked engine blocks.

Smokes from Exhaust

For cracks on the top of your engine block, the coolant or oil may invade the cylinder to foul its spark plugs. Misfire will ensue, leading to excessive smoke coming straight through the car’s exhaust pipe.

Overheating Engine

Engine cracks and coolant leakages often go hand in hand. As there’s a severe absence/lack of coolant, it’s no surprise that your engine easily becomes overheated

Some models install a modern check engine lighting system, where the light will flicker to inform you that the engine has grown too hot.

Frozen Coolants

A total opposite of overheating engines, this issue might occur to car drivers that live in colder climates. The radiator coolant may turn frozen, cracking and splitting the engine.

Frozen coolants are one of the most tell-tale signs – and easy to recognize through naked eyes. Stop the car and step down to check on them!

Worsened Engine Compression 

Every car engine requires good fuel and air mixture in small volumes for proper operation.

That’s why when holes take place, air leakage is inevitable, leading to extremely low compression. Don’t be surprised if power loss, bad fuel economy, and frequent engine misfires come your way! 

How to Fix Crack in Engine Block? 

hole in engine block repair cost
To Repair Engine Crack Repair

In most cases, they are impossible to fix, forcing you to turn to the only solution available: engine block replacements.

However, the answer might depend on other important factors (What is the hole size? Has the issue already wreaked havoc on other engine components?).

Hence, some lucky drivers still have an engine hole small enough to warrant quick fixes.

Engine Crack Repair At Auto Shop

First, find a good mechanic that understands what he is doing.

Have him work on the engine; the entire block must be torn apart, disassembled, and pulled off.

Then, the technician will closely examine each compartment, assess the damage severity, and devise a good solution.

Cracked Block Repair At Home Using Epoxy

Note: Only for skilled drivers.

Step 1. Prepare Your Engine Block

Prepare the surface properly before you start by:

  • Use soap, water, or degreaser solutions to clean it thoroughly
  • Remove oils, dirt, and contaminants that might affect epoxy adhesion. 
  • Please wait until it’s dry and clean, then sand the surface lightly with sandpaper (preferably fine-grit).

These techniques will help create a smooth, uniform surface.

Step 2. Mix The Epoxy

Each epoxy solution arrives with detailed package instructions; follow what’s written there to mix epoxy parts properly.

Avoid using too little or too much; improper mixing may lead to poor adhesion or uneven coverage.

Step 3. Apply The Epoxy 

Work fast; use a roller or foam brush to spread the solution evenly across the block’s entire surface.

Pick one end to start and move your hands from there, letting every stroke overlap to ensure consistent applications.

Let each epoxy coat dry completely (usually half an hour) before drafting a new layer. Three coats in total should offer enough protection.

Step 4. Finish Up

Sand the dry epoxy with sandpaper to foster a smoother finish. Once done, wipe away excess debris and dust using a clean rag. The engine is ready now! 

Step 5. Cure The Epoxy

Let the applied epoxy sit for 3 to 5 days at room temp before use. It ensures all epoxy layers are cured properly, providing durable and strong protection.

What Is The Hole in Engine Block Repair Cost?

Brace yourself for the off-the-roof charge that an engine block crack repair might ask from you.

That’s understandable, though; disassembling and assembling an engine block is by no means a smooth process! 

Expect to spend $1500 to $4000 for the simplest repair task. No wonder some people rather replace the entire engine block than fix it! 


Can You Weld The Engine Block?

Yes, though it’s not easy. The iron’s temperamental nature is quite a pain to work with.

Can I Drive My Car With A Hole in The Engine Block?

Yes, but only for a short while. It’s not recommended anyway; driving with broken blocks is too dangerous!

Can I Use JB to Weld Engine Blocks?

Yes. Like epoxy, JB is a pretty good sealant for engine blocks.

Do Cracked Engines Have Lower Energy/Power?

Obviously yes; most of it has escaped through the block crack!


A hole in engine block is horrifying, but fortunately, we have no shortage of tips to repair it.

And even if you can’t fix the issue, engine block replacements are still an option, anyway! Write to us if you need more help.

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