DIY

The Top 7 Symptoms of a Cracked Cylinder Head

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All too often, DIYers (and even some professionals) misdiagnose a cracked cylinder head as a blown head gasket. The mistake is easy to make since the two problems share many of the same symptoms.

A cracked cylinder head is a problem you’ll want to address right away to avoid further damaging the vehicle. Do you think your car might have a cracked head? If you’re noticing one or more of the symptoms below, you might be right.

Common Signs of a Cracked Head

engine cylinder head isolated on white background
The cylinder head seals the tops of the cylinders inside the engine block.

All engines have one or more cylinder heads. Engines with a ‘V’ or flat configuration have two cylinder heads, whereas engines with an inline or straight configuration have one.

The cylinder head seals the tops of the cylinders inside the engine block. Also, the head contains the valves (and sometimes the camshafts), which allow the air/fuel mixture to enter the engine and exhaust gases to exit. A head gasket provides a seal between the engine block and cylinder head.

A cracked cylinder head often exhibits the same symptoms as a blown head gasket. So, whenever you (or your mechanic) are doing a head gasket job, the heads should be checked for cracks by a machine shop prior to reinstallation. Machine shops have special tools and equipment that can detect cylinder head cracks that are not visible to the naked eye.

If your car is indeed suffering from a cracked cylinder head, you’ll likely notice one or more of the following symptoms:

White Smoke (Steam) From the Exhaust Pipe

There are coolant passages that run through the cylinder head. A crack in the head can allow coolant from those passages to leak into the engine’s combustion chamber, where the coolant is then burned during the combustion process.

combustion fumes coming out of car exhaust pipe
A crack in the head can allow coolant from the coolant passages to leak into the engine’s combustion chamber.

As a result, you’ll see white smoke, which is actually steam, coming out of the vehicle’s tailpipe. You may also notice that the exhaust fumes smell sweet.

Low Coolant Level

If the crack in the cylinder head allows coolant to enter (and be burned) inside of the combustion chamber, you may notice that the coolant level begins to drop.

Engine Overheating

A crack cylinder head may allow coolant to enter the combustion chamber instead of properly circulating through the engine. The engine may start to overheat as a result.

Rough Running and Misfiring

An engine needs three ingredients for complete combustion: proper spark, the correct air/fuel ratio, and adequate compression. A cracked cylinder head can result in a loss of compression that causes the engine to run rough and misfire.

mechanic checking car hood
A cracked cylinder head can result in a loss of compression that causes the engine to run rough and misfire.

Combustion Gases In the Cooling System

A cracked cylinder head can allow combustion gases to enter the cooling system. As a result, you may notice an excessive amount of bubbles in the coolant before it begins to boil. You may also notice that the cooling system is under extreme pressure.

Illuminated Warning Lights

A cracked cylinder head can trigger the check engine light, low coolant level light, and the engine over-temperature light. If your car is equipped with a temperature gauge, you may also see it begin to climb.

Check Engine Light lit up on a dashboard
A cracked cylinder head can trigger the check engine light, low coolant level light, and the engine over-temperature light.

Coolant-Oil Intermix

In some cases, a cracked cylinder head can result in coolant-oil intermix. Select Saturn models with the 1.9L single overhead camshaft engine are well-known for winding up with cracked cylinder heads that cause coolant-oil intermix.  

What Causes a Cylinder Head to Crack?

Some cylinder heads, such as those found on the Saturn engines mentioned above, can develop cracks due to design flaws. But the problem usually stems from engine overheating. When the engine gets too hot, the cylinder head cracks as a result of thermal stress. Allowing your engine to overheat even once can result in a cracked cylinder head.

Car engine cylinder head in white background
When the engine gets too hot, the cylinder head cracks as a result of thermal stress.

Cracked Cylinder Head Repair Cost

Repairing cracked cylinder heads is generally a thing of the past. Nowadays, since most modern heads are made from aluminum, nearly all shops will replace a cracked head rather than trying to repair it.

If you choose to have a professional replace your car’s cylinder head, you can usually expect to pay somewhere between $1000 and $2,500 per head. Of course, the exact price will depend on various factors, such as the year, make, and model of your vehicle.

It’s also worth noting that, sometimes, a crack cylinder head will cause additional damage to other parts of the engine. In such a scenario, you’ll likely have to rebuild or replace the entire engine.

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