What To Do About A Cracked Engine Block

One of the scariest things a car owner can experience is having a cracked engine block. While in some circumstances you can still drive the car, it will lead to much bigger problems later on.

We sat down with our performance shops pros to get their insight on the symptoms of a cracked block, how blocks crack, and what you can do if you are unfortunate enough to have one. ​​​​​​

How Do Engine Blocks Crack?

In South Florida, the most common cause of engine block cracks is the heat.

Your car’s engine will naturally experience quite a high heat from running, and when coupled with Florida’s notoriously hot weather, cars can begin to overheat. This overheating causes the block to experience heat’s the manufacturer never intended which causes the metal inside the engine block to expand and crack.

The second most common cause we find is poorly modified engines or engines that haven’t been properly maintained.

When engines haven’t been properly maintained, the oil becomes too thick and doesn’t lubricate the engine properly and that causes moving parts to get jammed. The jam doesn’t stop other parts from moving, and the forces being applied can cause parts like rods to bend out of shape and hit against the walls of the engine and crack the block.

Similarly, cars that have been poorly modified and are creating more power than the stock pistons and rods are designed for can cause the rods to bend and hit the engine block, which causes cracking.

How To Identify a Cracked Engine Block

This initial telltale sounds that an engine block may be cracked is that the car begins to overheat, simply not start, begin to leak oil or coolant on the ground, or your car will start producing heavy clouds of blue-gray smoke. These symptoms can be caused by other issues, but it does signify that you need to have a look under the hood.

The easiest way to physically spot a crack in the engine block is to check the color of the oil under the oil cap. Once the cap is removed, if the oil has the color and appearance of chocolate milk, it means that there is a crack in your engine’s coolant lines, and coolant is leaking into your oil.

If your oil looks normal, the next step is to start your car, let it warm up to operating temperature and then begin inspecting the engine bay. If you begin to see oil or coolant begin to drip or spray out of the block, you’ve identified a crack.

Repairing a Cracked Engine Block

In an emergency where you need to get your car home or to a mechanic, and assuming your crack is small enough, crack sealers such as Blue Devil, can temporarily block a crack and stop it from leaking. Ideally, you will need to get the crack professionally repaired.

A professional repair requires the engine the car and stripped to just the block. The block is then pressure tested to see if the block is viable for a repair. If it’s viable, the crack is then cleaned out and welded shut, or the cylinders and coolant paths can be machined to allow a plug or sleeve to be fitted. Unfortunately, if the crack has been left for too long, and is too large that the block’s integrity is compromised, the entire block will need to be replaced.

If you suspect your engine block might be cracked, or if you have any additional questions on engine repair or modification, look no further than Foreign Affairs Motorsport, South Florida’s Premier European Auto Repair, Performance & Race Facility Since 1978.