5 Symptoms of a Cracked Cylinder Head (and Repair Cost)

A cylinder head is the “top end” of the engine. It mates to the engine block to seal off the combustion chamber, which is where the engine burns fuel to make power.

Cylinder heads also house the valves that direct airflow. Intake valves draw in fresh air, combustion occurs, then exhaust valves allow the burnt air fuel mixture to exit the combustion chamber. An internal combustion engine is basically just a fancy air pump.

Under extreme conditions, a cylinder head can actually crack. A cracked cylinder head may yield similar symptoms to a blown head gasket or a cracked block, but is more expensive to fix than a blown head gasket. The solution is usually to buy a new cylinder head.

four stroke gasoline engine

What Causes a Cracked Cylinder Head?

1) Overheating

engine overheating symptoms

Internal combustion engines heat up very quickly. As the name implies, they are designed to contain small, controlled explosions.

Much of the energy in the combustion process is actually lost to thermal energy, instead of being converted into kinetic energy to power the vehicle. This is a byproduct of their design that can be mitigated, but never eliminated entirely.

The number one cause of a cracked cylinder head is overheating. When an engine overheats, its components may be stressed far beyond the heat threshold it was designed to withstand.

Since most heads are made out of aluminum, they may warp or crack when the engine gets hot enough.

An engine may overheat from a number of reasons, most of which are due to a failed component in the cooling system. Some possible causes are outlined below.

2) Air in the Cooling System

infrared engine temperature

Air in the cooling system may allow hot spots to form, where one part of the engine is much hotter than the portion measured by the temperature sensor. This happens because air cannot transfer heat as effectively as a liquid can.

If air is trapped in one spot away from the coolant temperature sensor, the temperature sensor may not pick up the hot spot. You may not know your car is running hot until damage is already done.

Additionally, an air leak in the cooling system may reduce the pressure in the cooling system. Liquid coolant is more likely to boil at a lower pressure.

3) Failed Water Pump

bad water pump

If the water pump fails, coolant won’t be able to circulate through the engine properly. The coolant in the radiator may be nice and cold, but the coolant surrounding the water jackets in the head and block will be extremely hot.

Without a pump, coolant will only be able to circulate via the natural convection process, which is much too slow to remove excess heat before the engine overheats.

4) Failed Thermostat

bad thermostat

Combustion engines are most efficient when they are running at the operating temperature they were designed for.

An engine’s normal operating temperature is still plenty hot enough to scald you – typically around 190 to 210 degrees Fahrenheit (85 to 99 degrees Celsius). Running the engine below this temperature increases fuel consumption, emissions, and wear.

A thermostat blocks off coolant from the radiator until the coolant in the engine reaches the target temperature. Once the target temperature is reached, the thermostat opens to allow coolant at ambient temperature to enter the engine, cooling it until the thermostat is cold enough to close. The cycle continues as the engine runs. 

If the thermostat is stuck open, your car will probably run pretty cold. This is because the coolant from the entire system is cycling through the radiator 100% of the time and rarely gets a chance to fully warm up.

If the thermostat is stuck closed, your engine will overheat pretty easily. The hot coolant has nowhere to go to cool off. In a pinch, some engines allow you to use the heater as a tiny radiator.

The effectiveness of this method depends on the size of the heater core and how the cooling system is routed.

5) Coolant Leak

coolant leaking

If too much coolant leaks out, eventually you won’t have enough to properly cool the engine. You can lose a decent amount of coolant before overheating, but it’s a good idea to regularly check the overflow reservoir and radiator to make sure you’re topped off.

If you notice a coolant leak, it’s a great idea to check your radiator cap. It’s a cheap part with some serious repercussions if it fails. Keep in mind that not all coolant leaks are visible.

Warning: The radiator of a warm engine is under pressure. Do not open the radiator cap on a warm engine!

Cracked Cylinder Head Symptoms

A minor crack in the cylinder head may go unnoticed for some time, but the symptoms will be pretty obvious in severe cases. Below are five common symptoms to watch out for in the event that this happens.

1) Oil Leak

oil leak

A cylinder head contains oil in it. If you have a cracked head, you can expect oil to leak out of it. You should notice the oil light on your dashboard turning on when this happens indicating a low oil pressure.

If you see this light on, open your hood and try to see if there’s engine oil near the cylinder head.

Sometimes oil will leak internally. When this happens, you won’t notice a puddle of oil, but may see blue smoke out the exhaust

2) Coolant Leak

coolant leaking

Although a coolant leak can cause a cracked head, it is also a symptom. If the cylinder head is severely cracked, then you’ll probably have coolant leaking out of it in addition to oil.

This will cause your engine to overheat, which your car will warn you about on your dashboard. Sometimes coolant leaks are internal. Internal leaks may leak into the oil passages or the combustion chamber. 

Either way, check your coolant level and do not continue to drive when you have a visible coolant leak or notice the coolant level quickly dropping over time.

3) Poor Engine Performance

car hesitates when accelerating - gas pedal

The first symptom you might experience is a noticeable loss in engine power. If the cylinder head has a crack, that means compressed air is escaping from the combustion chamber.

You will notice the engine running a lot slower or awkwardly once this happens.

4) Smoke From Engine

white smoke from exhaust

Although this is rare, big cracks in the cylinder heads will allow coolant to leak into the combustion chamber and cause white smoke to come from the engine.

In addition, leaking oil can make contact with hot engine components to produce this smoke. This is clearly a sign that a cracked cylinder head may be at fault.

5) Engine Misfire

engine misfire causes

This relates to number three. If the cracked cylinder head is severe, then the mixture in the combustion chamber will cause a misfire. This means the mixture won’t burn like it should.

Either that, or your engine will simply die as you’re driving and you will have to repeatedly start it back up.

Cracked Cylinder Head Repair Cost

The cost of a cracked cylinder head repair job will vary depending on the make and model of the vehicle that it’s in. You can be sure that it will cost at least $500, which includes labor and parts costs.

If you were to replace the entire cylinder head, it would only cost $200 to $300 on average for parts. With labor at about $90 to $100 per hour, this comes out to roughly $500 for the job. However, this is assuming the cylinder head is made of aluminum like they are in most cars these days.

If the cylinder heads are hard to access (as they are on Subarus, since they use a boxer engine layout), labor costs may be significantly higher. 

If you have an older vehicle or more expensive vehicle, you probably have a cylinder head made of iron. Since iron is a more expensive material than aluminum, you might be looking at $500 just for the parts.

The labor may also require more hours for this repair job to be done correctly. Therefore, you could be looking at $1,000 to repair a cracked cylinder head made of iron.

Kevin

31 thoughts on “5 Symptoms of a Cracked Cylinder Head (and Repair Cost)”

  1. I have a 97 mustang G.T 4.6 it was running little ruff thought it was fuel injectors so i replaced them when i started it now it really rus ruff with white smoke comming out the back. i am sure its a blown head gasket or crack. but how could that happen just because i replaced the injectors.

    Reply
    • I don’t think replacing the injectors would cause that. First identify the problem (i.e. make sure you know for sure that it is a bad head gasket), then you can figure out what caused it.

      Reply
  2. My 2021 canyon Denali had to be towed to a dealer because it quit running. I had to keep my foot to the floor to keep it running to get it to my neighborhood garage. He took a look at it and said it needed to be hauled to a dealer because it was still under warranty. So I had it towed to a dealer and they informed me that a valve broke and it ruined the cylinder. Does that happen often to new trucks with 20,000 miles on it and what should they do to fix it? I do not want them patching it and me getting it back and having this happen again after the warranty expires. I would like to have a little knowledge of what needs to be done to it so I can ask them if it is being done.

    Reply
  3. I have a 2014 grand cherokee limited. I’ve learned that it has a leak in cylinder 2. Should I replace the cylinder head? Or replace the whole motor?

    Reply
    • Do you know where the leak is coming from? If not, a leak down test may help you determine next steps and which components need replacing.

      Reply
  4. Hi, my Jeep KJ just lost pressure to coolant/radiator due to leaking overflow, fan made a whining sound for a few days then engine overheated and now loss of compression, loss of at least 1 cylinder. I fixed, pressure ok, not Casket as no white smoke, no overheating, no froth on oil cap. Crack or warped something?

    Reply
    • Not sure. If it overheated it could be anything. I think it’d be best to do a leak down test to figure out where you’re losing compression and go from there.

      Reply
  5. My 2006 Jeep Wrangler had crack in radiator. Car had no power. Gauges didn’t tell me about any overheating. Had new radiator put in. Car went for about 2-3 weeks but now and then had problem turning engine over when starting. Went out of town for a month. Car stood. Came back to drive it again. Nothing. Won’t start at all. Battery etc. good. What do you think it is?

    Reply
  6. my 1994 ford bronco has lots of white smoke coming from the exhaust i can smell coolant, and faintly hear a slight ticking, the motor was just rebuilt tell than 4,000 miles ago. how do i know if its a cracked intake or cracked heads or maybe a blown head gasket.

    Reply
  7. I have a 2007 Hyundai Sonata and when I turn it on, the engine makes a clicking/ticking noise? It sounds like it is coming from the top of the engine but can’t tell exactly what it is. What could cause this issue? Thank you.

    Reply
  8. I took my 2014 Totota Corolla S to Autozone yesterday (7/7/20) and performed the check engine light test. A few different things came up. What are the signs for a cracked cylinder head and is this vehicle too new for it to happen?

    Reply
    • Any car could potentially crack a head, no matter how new, if it overheated badly enough. However cracked heads are actually pretty rare so I doubt that’s the issue. What were the codes?

      Reply
  9. The cylinder head should crack in about 5 yrs? That just dosen’t sound right. 2004 pt Cruiser, are they known for the head cracking or warping?

    Reply
    • 1) A cylinder head should never crack but it happens.

      2) Some vehicles have a reputation for cracking heads but engineering flaws.

      3) If your PT Cruiser is a turbo charged model it will be much more prone to cracking because of the additional pressure inside the block.

      Reply
  10. Our truck is s10 2002 had a crack and been in the shop for 2 weeks, how long does it usually take to get it fix n how much will it cost?

    Reply
    • Every shop is different. A good part of that time could simply be waiting for parts to come in. Cylinder head repair/replacement is not cheap. Did the shop not give you an estimate?

      Reply
    • I did my own in the street, it took two days to remove the old one and fit the new one. I’m not a mechanic of any kind but I’ve had an interest in bikes, cars and trucks since my late teens. Why a garage would keep you waiting two weeks I can only guess unless like the other poster said they’re having problems getting parts.

      Reply

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