What Happens When an Engine Block Fails?
In the words of Maria Von Trapp, “Let’s start at the very beginning, a very good place to start.”

What on earth is an engine block anyway?

The engine block could be seen as the heart of the engine, there are all sorts of things pumping and flowing through it. It is full of cylinders and hoses and even an oil plan. Pretty much anything that keeps your car running travels through the engine block. It is an important piece of machinery that is designed to last the lifetime of your car.

And yet, sometimes the best-laid plans don’t work out. Those heavy-duty engine blocks can have some struggles and those struggles can wreak havoc on your engine.

What do those struggles look like? There are three main problems most cars might have with their engine block. Luckily, all these problems are uncommon. Still, since they can lead to major engine damage, it is valuable to know the signs of engine block trouble.

1. Porous Engine Block

A big, heavy engine block doesn’t seem like it would be very porous, right? There are plenty of holes, but those are to house specific working parts of the engine. The actual metal of the engine block is designed to be strong, heat resistant, and sturdy.

However, once in a very rare while, a bit of air might sneak into the process of molding the engine block and that can create a more porous metal. When you are dealing with essential fluids, like coolant and oil, porous is the last thing you want.

The good news with this flaw is that you might not ever even know about it. A porous engine block might cause such a minute amount of leaks, that it possibly won’t cause any trouble at all. Your fluids might get low with more frequency, but everything will hum along fine.

The bad news? If it does cause serious trouble there is pretty much nothing you can do about it. A porous engine block is simply a lemon from the start, and there is no repairing it, only replacing it. Replacing an engine block, in some cases, means replacing the car itself.

2. Cylinder Trouble

The cylinders house the pistons. The pistons’ movements convert fuel into energy for the crankshaft to move the tires. The tires get you where you want to go. To sum up: those cylinders matter. They need to be just the right size for the pistons to make the perfect seal and build up enough pressure to get everything moving.

If the engine block expands at all, making those cylinders too big, then the pistons will rattle around and do very little to get your car moving. Luckily, this is actually a problem that can be addressed. There are aluminum sleeves that can be fitted to your engine block cylinders to tighten them up for those pistons.

If, however, the cylinder is cracked, that is a bigger fish to fry. Depending on the location and size of the crack, it might be repairable. It won’t be cheap though, and it is always a balance between the value of the car and the cost of a repair.

3. Cracked

Of these uncommon problems, this one is the most common problem. A cracked engine block has left many people stranded on the side of the road. It isn’t the news you want to hear in a mechanic’s waiting room. Often, it can blindside you, but there are some warning signs. And if you catch a crack early enough, repair is possible.

The engine block deals with A LOT of heat. All that pumping and working heats stuff up. To keep things from overheating, you put coolant in your engine. If there is a crack in that engine block, the coolant will leak. If the coolant is leaking, then the engine will overheat. And that can lead to a total system failure and a very bad day.

Pay attention to a car that seems to be overheating regularly. That engine block could use some attention.

Another sign of a cracked engine block is excessive engine smoke or low compression. This can be due to fluids mixing that aren’t supposed to mix, such as oil and antifreeze. That cocktail can send off some bad exhaust fumes as the engine limps along.

Low compression will feel “off.” The car turns over but doesn’t start, or misfires and runs roughly. These are signs that cracks are keeping the pistons from sealing well, so the cracks are probably in the cylinders.

So, What Do I Do Now?

Just like you should never google “spider bite” images, looking up signs and symptoms of engine block failure can be pretty terrifying. We get colds more often than pneumonia, and most car troubles come from more minor issues than a cracked engine block. No need to panic.

That said, if there is a steady leak happening, take a look at that engine block while you are inspecting all the hoses. Most likely the leak is coming from an easier place, but it won’t hurt you to inspect the engine block while you’re having someone take a look. It’s also helpful to remember that a cracked engine block is not a death sentence. If caught early, it can often be repaired.

If you are car shopping, this engine block education will be helpful! Whether you are looking for a used car or a rebuilt title car, it is valuable to take a very good look at the engine block, whether on your own or with a trusted mechanic. Also ask questions about past damages and repairs to the engine block, paying attention to the sound of the engine as you test drive. Knowledge is power and can save you time, trouble, and stress down the road!


Since so many different things are pumping and flowing through the engine block, one may consider it the engine’s heart. The engine block is essentially the conduit for everything that keeps your automobile going. It is an essential piece of equipment that is built to last for the whole life of your automobile.
What Happens When an Engine Block Fails?