A cracked engine block is one of the most serious and costly issues you may encounter as a car owner. This could be mistaken for a blown head gasket or even a cracked cylinder head because it presents with some of the same symptoms. Unfortunately, a cracked engine block is much worse and usually means you need a completely new engine.
The Most Common Symptoms of cracked engine block are overheating, poor engine performance, coolant or oil leaks, and any evidence of those two liquids mixing.
If you’ve been informed that your engine block is cracked, you’re going to need to fix it sooner rather than later.
Not only is this article going to discuss everything you need to know about a cracked engine block, but it will also discuss what the cost is to fix it, if it’s safe to drive with a cracked one, and if your car’s performance is going to change.
Table of Contents
What Is An Engine Block?
An engine block is a cast iron casting that acts as the bottom part of the engine. This is where the cylinder head(s) and other major engine components are located. Not only that, but the block houses the pistons, connecting rods, crankshaft, and occasionally the camshaft.
The block and all internal parts can also be known as the “bottom end” of the engine. On the other hand, the cylinder head(s) and related parts are considered to be the “top end” of the engine.
Symptoms Of A Cracked Engine Block
A cracked engine block symptoms include poor performance, oil, and coolant leaks, evidence of those two liquids mixing, and overheating.
Even though a cracked engine block is pretty uncommon, the cylinder head(s) crack will begin to cause issues long before the block does. However, when the block cracks, there will be recognizable symptoms.
1. White Smoke From The Exhaust Pipe
Since coolant runs through the engine block via passages, a crack in the block can allow coolant to leak into the engine’s cylinders. The coolant is then burned during the combustion process. Because of this, you’ll see white smoke, which is steam, coming from the tailpipe. You may also smell the sweetness of the coolant in the fumes.
2. Fluid Leaks & Mixing
An engine block with a crack in it can result in internal and external leaks of coolant. Oil leaking from the block externally is a possibility as well, depending on where the crack is. You may also notice that coolant and oil are mixed.
This is a high indication of a cracked engine block. You’ll most likely notice this when you change your oil or check the dipstick.
3. Poor Performance
Have you noticed that your car is running poorly? If so, a cracked engine block could be the culprit. A cracked engine block can cause a loss of compression in the engine that causes it to run roughly and misfire.
4. Combustion Gases
Combustion gases can enter the cooling system through a cracked engine block. Because of this, you may see a lot of bubbles in the coolant before it starts to boil. You may also notice that your cooling system pressure levels are at an extreme high.
Since a cracked engine block can result in the loss of coolant, whether external or internal, it can prevent the coolant from circulating through the engine. As a result of this, the engine will begin to overheat.
6. Warning Lights
Most, if not all of the symptoms above can trigger your car’s warning lights on the dashboard. This includes the check engine light, low coolant light, and over-temperature light. If your car has a temperature gauge, this can also climb.
Diagnosing A Cracked Engine Block
There are several ways you or your mechanic can check your engine for a cracked block. Different methods will work with different parts of the motor (internal or external). Here are some of the most common diagnostic procedures that may be used.
An engine block with an external coolant leak can be diagnosed by performing a pressure test within the cooling system. This method involves pressurizing the coolant system with a dedicated pressure tester to find the exact source of the leak.
The system pressure tester can be used with a borescope to check for internal coolant leaks. You or your mechanic will remove the spark plug from the suspect cylinder and then insert the borescope into the hole where the sparkplug was. The cooling system will then be pressurized and the borescope will check for coolant leaking into the cylinder.
If coolant is found in the cylinder, it can point to a faulty head gasket, cracked cylinder head, or cracked engine block. To get a better look, the engine will need to be taken apart. Once it’s pulled apart, the block can be checked for cracks using a fluorescent dye and/or magnetic crack detection devices.
This device contains fluids that will change color in the presence of combustion gases. It can help detect a block that may be internally cracked. The tester will be placed over the cooling system filler neck. It will check for the presence of combustion gases within the cooling system.
If these gases are present, it means there’s a leak in the head gasket, the cylinder head is cracked, or the engine block is cracked. The engine will have to be taken apart to determine what the exact issue is.
Most of the time, you can spot a crack that’s leaking oil or coolant externally by performing a visual inspection of the block. You may notice pools of oil or coolant under the front of the car or you may notice a mixture of the two on the dipstick.
Why Do Engine Blocks Crack?
Engine blocks will crack as a result of overheating. The stress of expanding metal will become too much for the block to handle, so it will crack. You have to keep up on oil levels if necessary. This will keep the engine lubricated, cool, and free from sludge. This can all prevent overheating and cracks.
Additionally, a water pump failure can cause cracks to form in the engine block. The water pump can stop coolant from flowing through the system like it’s supposed to. This can cause severe overheating.
Alternatively, casting failure during the injection molding process can cause the metal of the engine block to be much thinner in certain areas. Once heat is applied to these areas, thin cracks may begin to form.
How Is A Cracked Engine Block Fixed?
Today, most mechanics will choose to replace the block or entire engine instead of repairing it. This may cost more, but it’s less time in the shop.
In the earlier days, a mechanic would fix a cracked engine block by welding, gluing, or pinning it, but not many shops will do this. It takes more time and could end up costing more in labor and parts.
How Much Does A Cracked Engine Block Cost To Repair?
It can cost between $1,500-$2,500 or more to repair a cracked engine block. For experienced mechanics, the figures below are approximate and exact costs have been excluded since they may vary based on region and the individual shop:
- Labor ($65-$125 per hour)
- Engine removal and disassembly (3-5 hours)
- Investigation and Diagnosis (as long as it takes)
- Welding (1-2 hours based on severity)
- Testing (depends on the testing method)
- Reassembly and replacement (3-5 hours)
- Welding materials ($50-$100)
Can You Drive With A Cracked Engine Block?
You may be able to drive a short distance with a cracked engine block, but you shouldn’t. A minor crack that’s barely leaking will be fine to drive with, but the only place you should go is to the mechanic. If you have a serious crack in the oil or coolant channels, it may still turn over and run, but shouldn’t be driven. Every minute the engine’s on, you risk doing even more damage to it.
If you don’t know whether or not it’s safe to drive your car, we suggest staying on the err side of caution. Call a mechanic or have your car towed. A cracked cylinder wall within the engine block may impact your vehicle’s performance so severely that the car will struggle to start. If this is the case, don’t ever drive it this way as it’s dangerous.
It’s best to take a preventative approach to avoid the situation. Make sure you’re changing your oil filter and oil along with keeping your coolant topped up. These are the two most important steps to ensure your motor lasts as long as possible.
Taking preventative measures will keep your engine solid and free of cracks. As we mentioned, it’s important to keep up on oil and oil filter changes as well as ensure there’s plenty of coolant in your engine.
If you notice any of the signs and symptoms above of a cracked engine block, get your car to a mechanic as soon as possible to avoid even more damage.
I’m William Guzenski, ASE certified master automobile technician & automotive expert. I love to attend race events and car shows throughout the country. I also loves to travel 40-foot motorhome, exploring abandoned mines and ghost towns. I’m currently building another car for Bonneville Salt Flats and will be campaigning a drag car at several events.