5 Symptoms of a Cracked Cylinder Head

A cylinder head is the "top end" of an engine and it mates to the engine block and seals off the combustion chamber, which is where the engine burns fuel to make the power. The cylinder head also houses the valves that direct airflow. The intake valves draw in fresh air, combustion then occurs, and then the exhaust valves allow the burnt air fuel mixture to exit the combustion chamber. An internal combustion engine is essentially an air pump.

Under some extreme conditions, a cylinder head can actually crack. Knowing the symptoms of a crack cylinder head can help diagnose the issue and bring it down to Thomas Auto for inspection and potential repair. Here are 5 areas to look out for in order to recognize a crack cylinder head.

Overheating

Overheating is the number one cause of a cracked cylinder head. When an engine overheats, its components may be stressed far beyond the heat threshold it was actually designed to withstand. Internal combustion engines heat up very quickly since 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 ultimately a byproduct of the design of the engine that can be mitigated, but never entirely eliminated. There are numerous reasons why an engine may overheat, but most have to do with a failed component in the cooling system.

Air in the Cooling System

If there is air in the cooling system, it may allow hot spots to form where one part of the engine is much hotter than the portion measured by the temperature sensor. This aspect happens because air cannot transfer heat as effectively as a liquid can. If the air is trapped in one spot away from the coolant temperature sensor, then the temperature sensor may not pick up the hot spot. So you might not know your car is running hot until the damage is already done. On top of that, an air leak in the cooling system can reduce the pressure in the cooling system. A liquid coolant is more likely to boil at a lower pressure.

Failed Water Pump

If the water pump fails, the coolant will not be able to circulate properly through the engine. The coolant in the radiator could be nice and cold, however the coolant surrounding the water jackets in the head and block will be very hot. Without a properly working pump, the coolant will only be able to circulate via the natural convection process. This process is too slow to remove any excess heat before the engine overheats.

Failed Thermostat

A combustion engine is most efficient when they are running at the operating temperature they were designed to handle. An engine's normal operating temperature is still plenty hot enough to burn you, since it is typically around 190 to 210 degrees Fahrenheit. Running the engine below this temperature will increase any fuel consumption, emissions and wear. What the thermostat does is block off the coolant from the radiator until the coolant in the engine reaches the target temperature. Once the temperature target is reached, the thermostat opens in order to allow coolant at ambient temperatures to enter the engine. Ultimately cooling the engine until the thermostat is cold enough to close. This cycle will continue as the engine runs.

However, if the thermostat is stuck open, then the car will probably run pretty cold. This is because the coolant from the entire system is cycling through the radiator one hundred percent of the time. So it rarely gets a chance to fully warm up. If the thermostat is stuck closed, then the engine will overheat pretty quickly. This is due to the fact that the hot coolant has nowhere to go to cool off. Sometimes an engine can allow the use of the heater as a tiny radiator. However, the size of the heater core and how the cooling system is routed impacts the effectiveness of this method.

Coolant Leak

If too much coolant leaks out of the engine, then you will eventually not have enough of it to properly cool it off. You can lose a decent amount of coolant before actually overheating. However, it is still a good idea to regularly check the overflow reservoir and radiator to make sure the engine is topped off. If you do notice a coolant leak, then checking the radiator cap is a good place to start. The radiator cap is a cheap part with some serious repercussions if it fails. Do not check the radiator cap on a warm engine, since the radiator of a warm engine is under pressure.

And it is important to note that not all coolant leaks are visible, which again adds emphasis to checking it periodically.

Contact Thomas Machine

Our repair shop has years of experience dealing with cylinder heads. Bring the cylinder head down to our shop and we can try to repair it, which will save you money from having to buy a new one. Our staff can find you the proper parts, as well as work on other aspects such as flywheel services and diesel engines. For more information about our cylinder head repairs and other services, please reach out to our office today.

When you reach out, we can go over the cylinder head repair work and provide you with a fair and accurate estimate. The cost for the cylinder head repair will vary on the make and model, but we will do our best to make the work as affordable as possible.