What Causes Cylinder Head Cracking?

Mary McMahon
Mary McMahon

The cylinder head is a crucial part of all combustion engines, and cylinder head cracking can result in catastrophic damage to the engine. In some cases, cracking may result in such severe injury to the engine that it must be replaced. As a result, most motorists try to prevent cylinder head cracking, as an ounce of prevention in this case is worth many pounds of cure. The causes of cracking are all relatively simple and easy to prevent, except in the case of mechanical parts failure through no fault of the operator.

Cylinder heads are an important part of a combustion engine.
Cylinder heads are an important part of a combustion engine.

The cylinder head, used in combination with a head gasket, seals the cylinders of the car, along with other parts associated with them. The cylinder head is customized for the vehicle, and has very precisely milled surfaces to provide a smooth and flush fit with all connecting parts. In the case of a minor crack, the cylinders may lose compression and misfire. Major cracks can cause severe damage to the cylinders of the engine. For this reason, when replacing either the cylinder head or the head gasket, make sure that you are using the correct parts, including bolts, for the job.

Pouring cold water into the radiator could result in a cracked cylinder head due to the extreme temperature change.
Pouring cold water into the radiator could result in a cracked cylinder head due to the extreme temperature change.

Even a brand new car can experience cylinder head cracking if parts have been installed incorrectly or if there are weaknesses in the metal. Especially in the case of a vehicle which is still under warranty, drivers should contest the condition with the dealer. Be certain to inspect any vehicle before you purchase to check for weak spots in the metal or incorrectly installed components. This includes the cylinder head gasket, because improper installation of this vital part can cause cylinder heads to crack.

Cylinder head cracks have become more common as car manufacturers use mixed metals in their engines. Many vehicles, for example, have a solid cast iron engine block but an aluminum cylinder head. These two metals expand at different rates, and this can lead to cylinder cracks.

The most common cause of a cracked cylinder head is overheating. When a vehicle overheats, it puts stress on all of its metal components, including the cylinder head, which is often at the center of the heat. This can cause the head gasket to fail, which may lead to cracking as the components warp and pressure begins to leak. All drivers should properly maintain their vehicles to prevent overheating.

Many drivers mistakenly pour cool water into the radiator when their vehicles overheat, in an attempt to bring the temperature down. This is not a good idea, because the rapid temperature change can cause cracks due to thermal stress. In a case where the cylinder head survives overheating, the driver may inadvertently destroy it by trying to do good.

To prevent overheating, make sure that your radiator is filled and in good condition, with a tightly sealed cap. Check to be certain that your engine thermostat is in good working order, and accurately reflecting the temperature. Make sure that you have no leaky belts or stretched hoses, and that the fan is working effectively. If your car does overheat, stop, turn off the engine, and allow it to cool completely before adding water.

A cracked cylinder head can also be caused by localized hot spots in the engine, which usually represent a failure in some portion of the cooling system. Always make sure that hot spots are addressed, particularly if your head gasket has failed and required replacement recently. Hot spots are often caused by uneven expansion of engine parts, leaky hoses, and pre-ignition in the cylinders of the engine.

If your car has overheated, check the cylinder head and gasket for signs of cracking or warping. If the cylinder head has warped even slightly out a flush state, it will cause cylinder head cracking. In this case, the head gasket may need to be replaced and the cylinder head should be ground even again before it cracks.

Overheating typically leads to cylinder head cracking.
Overheating typically leads to cylinder head cracking.
Mary McMahon
Mary McMahon

Ever since she began contributing to the site several years ago, Mary has embraced the exciting challenge of being a wiseGEEK researcher and writer. Mary has a liberal arts degree from Goddard College and spends her free time reading, cooking, and exploring the great outdoors.

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Discussion Comments


On the way home, my Skoda Octavia 2.0 2002 reg 8 valve petrol version decided that it needed to stop. I lost the power steering and brakes weren't working! I nearly had a crash. Luckily, the hand brake was in good working order.

At my favorite garage they said a cylinder head needs replacing. I will get a used one, but wonder how much longer my car will run.


I can't believe someone would blame the head on the mechanic's work. I'm not a 'pro' but am a very experienced (30 years). If they changed the water pump due to overheating, or the injectors, etc., because of a misfire, the damage was already done!

And yes, sometimes engines are defective at low mileage; that's why you get warranties. Problems with casting, although rare, can cause flow/hot spots and cause heat stress.


For the first time ever my 2006 Honda Ridgeline idled roughly upon starting. The engine light came on, for the first time ever.

I took it in to the dealer, as always, and the code showed misfiring on cylinder 4. They recommended replacing the spark plugs and the fuel injectors. They were fine at 95,000 miles. Later, they called and said I had a mixing of oil and fuel on cylinder 4 causing smoke to come out of my tailpipe. This was never before seen by me before I brought it in and it really pissed me off.

Honda paid for the work, which included o-rings, head gaskets, timing chain and water pump, spark plugs and fuel injectors, refilled oil and coolant. Three days later, I had the same problems as the first time. I believe they're trying to tell me my cylinder head is cracked. My vehicle has never run hot! Never! What's up?


I heard a teakettle noise, and the dealer put on a new radiator cap. It never overheated, but the engine light is on again. It always showed cylinder 1, did spark plugs, injector, and again the light came on, so I took it to the dealer again. They checked it out and said the oil (we did an oil change two weeks before -- mobile1 syn) was good stuff, and it had good gas. Then they stated it stemmed from the muffler. The van has 80,000 miles and is a 250 4x4. We bought it from dowling brand new, but they're telling me a 2003 is old. Grrr. Help!


How much do I need to buy a replacement for cylinder gasket for my toyota corolla?


I borrowed a friend's car the other evening and brought the car back to them. the next day they drove their car about 2 miles and lost all power, and i am now being blamed for "blowing the cylinders."

Is it possible they would know this without taking the engine head off? i know little about cars and feel they are trying to pull a fast one as they have had to get it jump started on two previous occasions last week.


I bought a Vauxhall Meriva 2005, March this year. 30.000 on the clock, ex mobility, less than five months and very little mileage. My car broke down and I've been told the cylinder head is cracked, due to overheating.

When I broke down, the RAC guy said it had lost water. He showed me the hose that leads from the radiator, and the other end of that hose had come off (not sure the name) and pointed to the clip that should have been attached at the end of the hose. In fact, it was halfway down the hose and by the looks of it, had been there quite a while, given the indentation it had made on the hose.

What I need to know is: do you think this was the cause of the cylinder head cracking? The water in the reservoir was full on the morning of my trip and I was only 45 minutes into my trip. Thanks.


i have a problem with my car. The water in the radiator is boiling and the thermostat goes up, and we need to add water from time to time. it's inconvenient for us if we're traveling long distances.


The mechanic just replaced water pump, timing belt, cam and crank shaft seals, alternator and power steering belts, thermostat, and valve pan cover gaskets. Now my car has blown a head gasket. Could the work the mechanic carried out have anything to do with the blown head gasket? It's a 1993 Toyota Windom 3.0. Please help.


I have a 2000 cadillac sts and the dealership is saying that I have a worn cylinder because the car smokes when cranked. this all happened when the car overheated like three times and they say it's not their fault.


waddoe, try another mechanic, and/or dealership. Get the input of several different shops/mechanics, because yeah, that's *crazy* to replace an engine of a vehicle with only 72K.


I have a 2004 Ford Freestar minivan. it has been leaking coolant. Was told I have a cracked head.

They want to replace the engine (which comes with a new head) because they said that replacing the only the head, does not fix any damage to the engine that may have occurred because of the crack. I have 72K miles on this van. I can't believe I really need to replace the engine... any advice?

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