Maybe. There are options, but it’s a big deal.

Quick Notes

– Cracked engine blocks are usually caused by extreme engine temperatures

– A cracked engine block can be fixed

– The quality and lifetime of the repair will depend upon the initial severity of the crack

Can you fix a cracked engine block? Yes, but success will depend on a variety of factors. The success of the repair will depend on whether one is mechanically inclined, the anticipated life and performance use of the repaired engine block, and the severity of the initial crack.

Engine block

The engine block is the largest part of the engine. It contains the pistons and cylinders, and paths through which oil and coolant are pumped. The engine block’s purpose is to support the parts of the engine and to transfer heat to the engine coolant to be dispersed.

A cracked engine block can be fixed, but it may not be a lasting fix depending on the severity of the crack. For those mechanically inclined it may be cheaper to replace or rebuild the engine.

Once there is a crack in the engine block, the concern is its ongoing structural stability once its integrity has been compromised.

This can cause issues with cylinders, crankcase, and fluid passages and other problems such as loss of performance and overheating.

How can you tell if the engine block is cracked?

1. Colored smoke – If the engine area starts smoking, it can be a sign that there is a crack in the engine block. The smoke would usually appear to be a blue or grey/black color.

2. Overheating engine – When a car overheats repeatedly it is a sign that the coolant is low. If there is a leak and the coolant is not circulating through the engine block, there may be a crack in the engine block causing the coolant to be redirected elsewhere.

3. Oil & coolant mixture – Oil and coolant operate in separate confined areas. If you see a build-up of white around the engine oil cap, the coolant and oil may be mixing together. A crack in the engine block would cause the coolant to leak into the engine oil causing the oil to become a milky white grease.

4. Loss of engine performance – A cracked engine block causes low engine compression, which will reflect in rough idling, greater fuel consumption, and general poor engine performance.

What causes an engine block to crack?

The most common reason for an engine block cracking is engine overheating. High heat causes the metal to expand, which can cause failure points in the metal.

1. High heat – Repeated high temperatures over time can lead to engine block cracking. The cause of engine overheating is often related to low engine coolant. Water pump failure is another. A water pump failure means the coolant is not being pumped through the engine to remove heat. An engine can also overheat when it is overpowered.

2. Low temperatures – Excessively low temperatures can also cause an engine block to crack. This would more commonly be seen in older vehicles using the old-style coolant. When coolant freezes it can expand and apply pressure to the walls of the engine block causing micro-cracks.

3. Manufacturer defect – A rare, but possible, reason for a cracked engine block is a manufacturer’s defect – a failure when the block was cast. When the engine block is manufactured, it is formed in a mold. A fault in the molding process can result in a thinner area or other flaws on the engine block leading to engine block cracking.

Fixing a cracked engine block


1. Commercial sealants – Sealants can be suitable for smaller cracks relating to an issue with the cooling system. The fix involves adding the sealant to the coolant. Over time the product works its way into the cracks and forms a permanent seal. This works for small cracks but would not be suitable for larger cracks.

2. Welding – An engine block can be re-welded to seal cracks. The engine block is one solid component. The repair requires special tools and should only be done by a licensed professional as welding can make the entire engine block more susceptible to cracking.

Welding also makes the engine block more susceptible to deformation which can undermine the structural integrity and safety of the engine block.

3. Cold welding patches – Patching involves the use of adhesives and epoxies to seal cracks in the engine block, often using these glues along with an actual patch. They should only be considered a short term solution as the high heat can damage the patching job leading to further engine block damage.

4. Cold Metal StitchingCold metal stitching is a very expensive process wherein the pieces of metal are stitched together similar to torn fabric. It is ineffective in high engine heat situations and should only be undertaken by a professional.

The severity of the crack will determine whether it can be fixed. Other factors include your driving usage. Leisure versus commuter usage will not only affect the successfulness of the solution but also driver satisfaction with it. If the car is used for daily long-distance commuting, these measures are unlikely to be an effective long term solution. Replacement may be a better option.

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