The majority of today’s engines consist of a four-stroke design that utilizes three fluids: combustible air fuel, water/glycol coolant and motor oil. None of these fluids can ever come into contact with each other. To ensure these fluids are properly routed between components with no intermixing, there’s the head gasket.
In this article:
- What is a Head Gasket?
- What are the Signs & Symptoms of a Blown Head Gasket?
- The Trouble with Ignoring Blown Head Gasket Symptoms
- How to Minimize Head Gasket Problems
- How to Tell if You Have a Blown Head Gasket
- Visual Signs of Blown Head Gasket Symptoms
- Can You Drive with a Blown Head Gasket?
- Is the Car Still Safe for Driving?
- How Much Does it Cost to Fix a Blown Head Gasket?
- Bar’s Leaks Solutions for a Blown Head Gasket
What Is a Head Gasket?
In automobile engines, the head gasket is a ringed panel that is placed between the cylinder head and engine block. The head gasket is put in place as a barrier that prevents engine fluids from leaking into the cylinders. As such, the head gasket is among the most vital components in the combustion chamber. In addition to serving as a barrier to the cylinder, the head gasket blocks off conduits to the oil and water. Due to its position between hot and cold engine components, the head gasket faces a full range of temperatures, from the high heat of the combustion chamber to the often cold temperatures of the cooling system. As the impacts of temperature changes take their toll over time, the head gasket can ultimately bear marks along the surface. Consequently, leaks do often develop along this crucial area. If the problem worsens, the gasket can blow — all of which begs the question: What is a blown head gasket?
What Are the Signs and Symptoms of a Blown Head Gasket?
A driver will often wonder what causes a blown head gasket. The truth is, anything from the coolant system to the combustion chamber could be responsible. Most confusing is the fact that symptoms which resemble those of head gasket failure will sometimes originate from other causes. In certain cases, a symptom might show due to multiple failures within the engine. Examples could include the following:
- Overheating could be caused by a restricted radiator, which can get worse the farther you drive along.
- Coolant in the oil, usually blamed on head gaskets, could actually be due to problems with the intake gasket.
The Trouble with Ignoring Blown Head Gasket SymptomsOften times, a driver will ignore blown head gasket symptoms due to the costs that come with repairs. This can be an even more costly mistake, however, because in many cases, blown head gaskets lead to further car trouble if you continue driving. A coolant leak, for example, could lead to the following problems:
- Damage to the catalytic converter
- Leaks into the engine oil, which can ruin the engine
- Erosion of lubrication
- Overheating caused by mixtures of coolant and combustion gases
Other Blown Head Gasket Signs? Maybe, Maybe NotSo why is it often hard to get an accurate diagnosis of a blown head gasket? A lot of the problem is due to the similarity between issues with head gaskets and other engine components, such as the following:
- A chipped or warped cylinder head, which could affect the head gasket, but wouldn’t necessarily be the result of a blown head gasket
- Corrosion at the surface of the head gasket, which would indicate a leak, but one that wouldn’t necessarily be due to a head gasket blown
Related Symptoms of Blown Head Gasket TroubleWhen head gasket failure occurs between two or more cylinders, several symptoms are bound to result. The most common symptom in this case is a misfire, which would result from the leakage of compression between cylinders. Evidence of this could include the following:
- Lowered compression due to rough idling
- Overheating of the engine
- Coolant leakage to the oil compartment
- Coolant on top of a spark plug
Overheating Due to a Blown Head GasketWhen the failure of a head gasket occurs between the cooling system and combustion chamber, the evidence is typically displayed by coolant loss and overheating problems. The latter symptom can be especially troubling because overheating often only shows in fits and starts, such as when a vehicle has been on the road for some distance. However, overheating can also do damage when it doesn’t become apparent, such as during short trips along slow roads. For example, if you drive from your house to the nearby grocery store, your car might not exceed 35 mph for the trip. Therefore, the car won’t reach the freeway speeds that would more likely agitate an overheating issue. Nonetheless, the problem will still simmer inside the engine, even if you don’t end up seeing the heat gauge spike or any smoke seep from the hood of the car. In cars where overheating does not become readily apparent, damages caused by combustion gasses could include the following:
- Damage to the cooling system
- Failure of the radiator
- Erosion of the hoses
Blown Head Gaskets and Nearby ComponentsAnother source of trouble is when a head gasket fails between the coolant and lubrication components. A telltale sign of this is when the fluid from one seeps into the other. Typically, the first symptom to show in such cases is when the radiator cap swells. However, the problem can be harder to spot in cars that use glycol oil, which is less likely to take on a milky appearance when corrupted. When a problem like this occurs, the viscosity of the oil is affected, and this will ultimately compromise the engine’s lubrication. While it’s common for head gasket failure to be misdiagnosed as something else, there are also times when a problem thought to be related to the head gasket and components nearby is actually its own matter entirely. An oil leak, for example, is something that often happens independently of the head gasket, which in itself is rarely a cause for such leaks. Worn valve covers, on the other hand, are often responsible for oil leaks — though not in all cases. As such, the following misperceptions often persist:
- The head gasket couldn’t possibly be responsible for an oil leak.
- If there’s an oil leak, it must be due to a faulty valve cover.
How to Test for a Blown Head GasketA reliable way to determine whether a head gasket is blown is to test for carbon dioxide. In this test, the coolant is examined for traces of combustion gasses. The test is performed with an apparatus that utilizes a solution that changes color upon contact with carbon monoxide. The steps are as follows:
- Lower the level of coolant in the radiator (to provide a testing air space).
- Warm the engine (for improved accuracy).
- Use the tool to extract fume samples from the coolant.
- Mix samples in testing solution.
If the solution turns yellow, the coolant has failed the test, which indicates a problem. Granted, the test doesn’t always work, and carbon dioxide could still be present in the coolant without a change in color to the solution. Nonetheless, the test is generally reliable at detecting a problem that is symptomatic of an unhealthy engine. Another problem that a carbon dioxide test could possibly reveal is a ruptured cylinder head, which causes similar symptoms to a failed head gasket. In many cases, a cylinder head crack will be too tiny for the human eye to spot, yet it could still be a major problem. At some repair shops, cracks are found with the use of dyes or the application of pressure tests. As with coolant tests, cylinder head testing is best done by a professional car technician.
Car Designs and Faulty Head GasketsIn overhead cam engines, the gasket can only be accessed by taking out the front and top of the engine, which usually entails removal of the timing chain or belt. In some makes and models, most of the engine must be removed in order to gain access to the head gasket. The failure of a head gasket is sometimes due to limitations in the vehicle’s engine design. Consequently, maintenance of the cooling system with quality fluid and top-ups is evermore essential in today’s cars. In modern engines, normal temperature levels place in the range of 200 to 225 °F. Therefore, when a temperature gauge rises to the hot zone, it means that the engine is really hot. If an engine rises above 240 °F, the head gasket and cooling system could both be pushed beyond their normal limits. If the engine soars past 260 °F, the impact is almost inevitable.
Another factor that can lead to gasket failure is low-grade fuel, which is often responsible for excess pressure on the cylinder head. This is due to detonation and pinging, which often occur when fuels with lower-than-recommended octane levels are used in an engine.
How to Minimize Head Gasket ProblemsIn order to minimize the chances of head gasket failure in your vehicle, perform the following steps accordingly:
- Before the coolant drops below a pH of 7.0, refill the reservoir.
- Use readymade coolant/water mixtures — never add the two separately.
- Cut the engine the moment it overheats.
- Examine and remedy the conditions of overheating. Have the engine professionally diagnosed if necessary.
How to Tell If You Have a Blown Head GasketDue to its obscured placement between components in the engine, the head gasket cannot be examined without major disassembling work. That means it’s hard to make a diagnosis on a gasket’s condition, but visual inspections are rarely useful at pinpointing head gasket problems anyway. The best way to diagnose a problem is to study the symptoms as they occur and have a knowledge of what they most likely mean. Common symptoms of a blown head gasket include the following:
- External leaks of coolant from under the exhaust gasket
- Overheating under the hood
- Smoke blowing from the exhaust with a white-ish tint
- Depleted coolant levels with no trace of leakage
- Bubble formations in the radiator and overflow compartment
- Milky discoloration of the oil
From a purely visual perspective, the most surefire evidence of a blown head gasket is the presence of leaked coolant along the gasket surface. In the majority of cases, leaks occur between the engine’s combustion and cooling components.
Visual Signs of Blown Head Gasket Symptoms
When the combustion chamber gets penetrated with coolant, the engine loses its equilibrium and its ability to keep heat levels from rising as the car moves faster along roads and freeways. As a result, the engine is likely to overheat unless the coolant is refilled on a constant basis. The problems don’t stop once you park the car, either. After the engine is shut off, coolant that lingers in the cylinder can leak into the engine oil. This newly corrupted oil will often assume a milky appearance that can usually be identified with an inspection of either the dipstick or cap rings. When the engine runs, white smoke will form from whatever is left of the coolant inside the combustion chamber. The smoke in question is easiest to identify on warm days, when it can often be seen blowing from the exhaust pipes as the car sits warm and idling. On cold and wet days, the smoke is harder to identify due to the increased likelihood of steam, which has a similar appearance. Alternately, symptoms such as these can be identified by certain smells. A sweet smell, for instance, is usually indicative of a head gasket problem. In the midst of all these problems, exhaust gases from the combustion chamber could enter the cooling system, where they’ll circulate and pass to the radiator. The easiest place to spot evidence of this is in the cooling tank, which may contain bubbles as a result of pressurization. The cooling system remains pressurized for as long as the engine is warm, so the radiator cap should never be removed while the engine is idling or has just recently been shut off. In short, some of the most telltale visual signs of a blown head gasket include:
- Milky Oil
- White exhaust
- Bubble formations along the cooling system
How to Spot Signs of Blown Head Gasket Trouble in Newer VehiclesIn today’s automobiles, the cylinder head contains various coolant passages, which allow heat from the engine to escape with each passing mile. The purpose of the head gasket is to prevent coolant from flowing through these passages into the combustion chamber. However, when the gasket ruptures, all goes awry:
- The engine gets flooded with coolant.
- The coolant gets consumed with exhaust gasses.
- The engine rapidly overheats.
- An overabundance of steam coming out of the exhaust pipe
- Bubble formations in the coolant reservoir
Oil Characteristics With a Blown Head GasketThe purpose of oil passages — which exist in equal proportion between the cooling system and cylinder head — is to allow for the transfer of oil from the cylinder into the train valve and back. When the head gasket blows, the engine consumes oil at excessive rates. Granted, cases of excess oil consumption can also be due to other causes, such as weakened piston rings. However, in a large number of vehicles, burning through oil much faster that an engine is supposed to within a given span of time is usually the result of a blown head gasket. Common symptoms of excess oil consumption include the following:
- Excessive exhaust with a faint blue or whitish tint
- Diminished idling ability
- Loss of proper viscosity
- Diminished ability to lubricate the engine and all of its moving parts
- Erosion of key engine parts and bearings
Can You Drive with a Blown Head Gasket?
Given the high costs associated with head gasket replacement, one of the most frequent questions that auto mechanics hear from drivers is “how long can you drive with a blown head gasket without doing serious damage to the engine?” It really all boils down to the severity of the problem. If you only see a slight loss of pressure under a hard load, you only have a slight problem with the head gasket. However, if you find yourself repeatedly adding coolant to the engine just to keep it from overheating, you’ve got a serious problem on your hand that will hardly be staved off with the stopgap method of coolant top-offs. Even if the engine doesn’t overheat, it could still incur irreparable damage over a short period of time if constantly placed under high-pressure conditions. People also wonder if it’s safe to drive a vehicle when the engine pushes coolant just slightly, but without evidence of gushing or clouds of white exhaust. The answer here is yes and no. In order to really know, you need to test the vehicle first.
How to Test a Head Gasket to See If the Car Is Still Safe for DrivingFor the following test and for as long as the engine has gasket problems, keep a few gallons of 50/50 coolant on hand. Cheap coolant will suffice in this experiment since it’s going to be flushed out of the engine anyway:
- Fill the coolant up and drive the car around with the coolant cap loose.
- Let the speed work its way up to about 50 mph.
- Drive around for an afternoon and see how much coolant the engine consumes during a 50-mile trip.
How Much Does It Cost to Fix a Blown Head Gasket?
Due to the deep placement of head gaskets in modern engines, the replacement costs for gaskets and cylinder heads are generally expensive. However, for cars that show only mild to moderate symptoms, low-cost alternatives do exist. Chief among these options is our award-winning, mechanic-tested range stop leak products, which can relieve you of your blown head gasket repair cost concerns. Bar’s Leaks has long provided professionally-proven chemical solutions to a range of car problems, from head gasket issues to coolant and oil leaks. When it comes to problems with the head gasket, repairs are often outside the budget range of the average driver. On older cars in particular, the investment required for a mechanical blown head gasket fix is often not worth it, considering the value of the car. For just a fraction of what you’d spend for an outright gasket replacement, our products will get your car back out on the road and driving again.
Bar’s Leaks Solutions for a Blown Head Gasket
By far the most common question we get on our tech lines and Facebook is: “How can I tell if your head gasket products will fix my head gasket leak? I’ve heard some of these products don’t work.” There is one bottom-line truth, no matter what any chemical tool company tells you: if your head gasket leak is too severe, no chemical repair will seal the leak. We’d love to tell you otherwise, but we’re always honest with our customers. If your leak too advanced, then you’re looking at a physical repair. But there are many steps between a healthy head gasket and a blown head gasket, and that’s where we come in. So, here’s how to tell if your blown head gasket is a good fit for one of our head gasket repair solutions:
Can your car run or be driven for 15 minutes without overheating?First, the bad news: if your vehicle cannot run for 15 minutes without overheating, your leak is probably too severe to be chemically sealed. In cases like this, there is less than a 50% chance we can help. If your vehicle can run for 15 minutes without overheating, then our strongest product, Bar’s Leaks Professional Head Seal Blown Head Gasket Repair (p/n HG-1) will probably work. HG-1 is our most expensive product, one that’s truly commercial-grade, but it’s also our strongest formula, designed for the toughest leaks. It’s also very easy to install, with no draining or flushing necessary unless the cooling system is dirty or partially clogged. But wait. Before you decide on our HG-1 product, there is another question:
Can your car run or be driven for 20 minutes without overheating?
If so, then you are likely a good fit for our Bar’s Leaks Head Gasket Fix (p/n 1111), one of our most wildly popular products. Why is it popular? It has a medium price point and is very easy to install because it’s antifreeze-compatible. Its sealing power is a bit below our HG-1 product, but the installation is quick and easy. For most moderate HG leaks, this product has worked for hundreds of thousands of customers. If you want a cheaper, but also strong product whose installation is a bit more involved, our Bar’s Leaks Head Gasket Repair (p/n 1100) is a great option. It offers a very strong seal and a lower price, but installation is more demanding because the formula is not compatible with antifreeze. So, basically speaking, this is how you can tell if one of our products can help with your blown head gasket:
- If your vehicle can run for 15 minutes without overheating and you need our most professional-grade solution, consider our HG-1 product.
- If your vehicle can run for 20 minutes without overheating, consider our 1111 product or 1100 product, depending on how easy you want the installation to be.
- The real, honest truth that most chemical repair companies won’t tell you: If your vehicle overheats within 15 minutes, chances are you need a hard-part repair by a qualified mechanic. We’d love to be able to sell you a product, but if your car is overheating rapidly, no chemical fix will work. It’s not just ours that probably won’t work, but any. Save your money for a mechanic’s attention.