What is a Head Gasket?
In an internal combustion engine, a head gasket provides the seal between the engine block and cylinder head(s). Its purpose is to seal the combustion gases within the cylinders and to avoid coolant or engine oil leaking into the cylinders. Leaks in the head gasket can cause poor engine running and/or overheating.
The head gasket is located between the cylinder head and the engine block. This small but important component is used to seal off the combustion process so that coolant and oil can flow through the engine for cooling and lubrication.
This means if it “blows” it can cause major problems for the engine. The symptoms of a blown head gasket are pretty easy to spot and need to be fixed pretty quickly to avoid damaging your engine.
In addition to sealing the combustion section of the engine to allow oil and coolant to circulate, the head gasket also seals the combustion chamber in the engine. This allows the vehicle to generate enough power to move forward and prevent harmful gases from leaking out of the combustion chamber by routing them through the exhaust system.
The head gasket in modern vehicles is made up of several layers of steel material intertwined with elastomer, making it more durable and long-lasting. Vehicles manufactured in the past were equipped with seals made of graphite or asbestos.
In comparison, today’s seals are better because they are less prone to leakage and, unlike asbestos-made seals, have little to no health risks.
The head gasket is an essential part of the combustible engine. The head gasket ensures that the pressure generated by the ignition of the fuel vapors by the spark plug remains in the combustion chamber. The combustion chamber contains the pistons and requires high pressure to ensure that the pistons continue to fire adequately.
In addition, oil and coolant have important roles to play, but they cannot mix in order to do their jobs efficiently. The head gasket keeps the chambers separate to ensure that no cross-contamination of the fluids occurs.
What Causes a Head Gasket to Blow?
The most common cause of a blown or damaged head gasket is often an overheated engine. High engine temperatures are usually caused by a lack of coolant in the radiator, usually due to a leak.
Some seals are likely to weaken sooner than others, depending on the material. For example, aluminum expands faster when heated. Metals with a higher rate of thermal expansion are more sensitive to heat.
Higher temperatures can cause the shape of the object to change, which leads to an unfavorable result. The expansion and deformation of the cylinder head due to heat weakens its integrity and prevents the head gasket from sealing properly.
If the head gasket has burned out, it is important that it be fixed immediately. Continuing to operate a vehicle with a blown seal can cause serious and irreparable damage to the engine. Since the gasket is used as a gasket, maintaining pressure is key to engine performance.
Once the seal burns out, it can no longer function as a seal and allows pressure to escape, significantly reducing engine performance. This is one of the few signs of a blown head gasket. Also, oil and coolant passages can get into areas they shouldn’t be.
When coolant gets into the combustion chambers, it mixes and dilutes the engine oil while reducing the cooling performance of the cooling system, which can cause the engine to overheat.
5 Signs You Have a Blown Head Gasket
Once a head gasket has failed it can cause all manner of problems, including:
A head gasket failure may have been caused by excessive engine overheating (as a result of a clogged radiator, coolant leak, defective fan, etc.). However, a blown head gasket will also overheat the engine.
Hot exhaust gases can leak into the cooling system, or coolant can leak into the cylinders and be burned as vapor. In either case, the end result is overheating of the engine.
If the car is driven while overheating, the alloy cylinder head can also warp, or steam can damage the catalytic converter, significantly increasing repair costs.
2) Loss Of Power
If the head gasket fails to allow compressed air / fuel to escape, the compression on that cylinder will be reduced. This loss of compression results in a rough engine running and a noticeable decrease in engine performance. This type of failure is usually accompanied by a noise such as an exhaust leak.
3) Oil Contamination
One of the most common signs of head gasket failure is the milk sludge on the bottom of the oil filler cap or dipstick, sometimes jokingly referred to as a “milkshake”. This is caused by coolant getting into the oil and vice versa.
While this is not conclusive evidence of head gasket failure, it is generally a good indicator and a sure sign that your engine must fall apart in order to find the source of the contamination.
If the oil becomes contaminated with antifreeze, the motor’s bearings are quickly destroyed with every trip. The repair will require at least an engine oil flush, replacement oil filter, and often a complete disassembly of the bottom end of the engine to ensure the bearings are not damaged and to remove any contaminated oil.
4) White Smoke
A faulty head gasket usually results in large clouds of sweet-smelling white smoke coming out of the exhaust. This is caused by antifreeze that gets past the seal into the cylinders and is converted into steam as part of the combustion process.
Less common, but still possible, is a leak from an oil passage to the cylinder, which would cause bluish smoke.
Each of these types of seal failure also allows for combustion pressure in the cooling system or the oil vent system. If a radiator hose suddenly blows its water outlet or the dipstick does not stay in place, this could be the cause.
5) External Leaks
If a head gasket fails between the water or oil passage and the outside of the engine, it can result in a simple coolant or oil leak. This is the least bad version of a blown head gasket, but it’s still serious.
This may not manifest itself as an immediate problem (other than causing a mess), but allowing the coolant level to drop too far can lead to serious engine problems. The other problem is that leaking oil can get into the hot exhaust and lead to acrid smoke and possible fire.
Preventing Head Gasket Failures
A few dollars of prevention is much better than the thousands of dollars cure when it comes to head gaskets. The replacement head gasket itself is inexpensive, but it is very labor-intensive to repair, which significantly increases repair costs, especially for modern cars.
Head gasket failures are usually caused by repeated overheating or by continuing to drive after the vehicle has overheated. The best way to prevent head gasket failure is to make sure that your cooling system is in good working order. And if your car boils over, stop, let it cool down for at least an hour, and then top up the radiator before continuing.
Checking the cooling system is simple: make sure there are no leaks, the radiator is working efficiently, the thermostat opens properly, and the coolant is topped up to the correct level. Also, make sure the fan (mechanical or electrical) is working, has all the blades, and has a cover around it to increase efficiency.
If you suspect head gasket failure, the scientific test is to check the cooling system for combustion gases. This test shows if the compression has gotten into the cooling system and therefore the head gasket has burned out. The old mechanic’s trick is to remove the radiator cap, start the car, and check for bubbles in the coolant.
However, these do not indicate whether there are other imperfections in the head gasket, so the absence of gases in the cooling system does not guarantee a healthy head gasket.
Some older head gaskets can simply fail because they are poorly designed and not tough enough to use. It used to be more of a problem with older metal seals that could only go from cold to hot for so many years before failing.
Fortunately, modern MLS (Multiple Layer Steel) replacement seals are now available for most applications and offer improved reliability over the original seal design.
Head Gasket Replacement
Replacing the head gasket is not a job for the average DIY enthusiast. While a head gasket leaking due to age is rare, it usually means everything else is worn out by the time it is replaced. If you crack the head off the engine and look inside it may turn out everything else has been fully cooked too.
The best way to prevent head gasket failure is to keep the cooling system in good working order and to make sure the engine is properly tuned and running. The failure of a $ 5 thermostat or $ 3 coolant hose can quickly cause thousands of dollars in engine damage.
6 Steps To Replacing A Head Gasket
The following are a few general tips to replace a head gasket. For vehicle-specific head gasket replacement procedures, always consult a service manual.
- Step 1: Getting down to the head gasket can be an involved process. Always mark and index everything before removal. In this case, it was easier to remove the exhaust manifold, head and intake as a unit. A service manual is the first and most important tool in the toolbox.
- Step 2: Check the head and block for flatness. A machined straight edge across the surface and feeler gauge will reveal all. The service manual will provide specifications. Blocks or heads out of specification must be sent out to the machine shop and be repaired. The machine shop will also be able to check for cracks.
- Step 3: Prepare the surface. Never use anything that will remove metal. Be careful not to scratch the deck of the block or mounting surface of the head. While it may seem like a good idea to use a scrubber pad connected to a power tool, the surface irregularities created can cause sealing problems down the road.
- Step 4: Chase the head bolt or stud holes with a tap or thread chaser to remove any crud and prepare the threads. Use compressed air to blow out any stragglers. Correct head bolt torque is of the utmost importance. Any interference can throw off the torque readings.
- Step 5: Prefit the head gasket in the correct orientation. Never use sealant unless specifically required by the manufacturer. Head gaskets that require sealant will usually come so equipped. The service manual will outline sealant locations and requirements.
- Step 6: Correct bolt tightening sequence and torque is key to proper head gasket sealing. Use new bolts if required. Coat head bolt threads with some engine oil before installing. Always follow tightening sequence and torque instructions to the last detail.
How much does a head gasket repair cost?
Repairing a blown head gasket is any motorist’s worst nightmare. If you’re starting to notice the tell-tale symptoms of a head gasket leak, you need to get it sorted to avoid costly repairs hitting you in the wallet.
How much does it cost to replace a blown head gasket?
The cost of repairing head gaskets can run into thousands, which means it is often easier and cheaper to scrap the vehicle than to have it repaired. The average cost to repair head gaskets ranges from $ 1,000 to $2,000. However, this is not because the parts are expensive.
Why do head gasket repairs cost so much?
The high cost of repairing the head gasket generally results from the labor required to correct the problem rather than the cost of a replacement part. Replacing your head gasket is an extremely time-consuming task as the motorhead must be removed and then replaced.
And the more time a mechanic has to spend on this job rather than anything else, the more they’ll charge you.
Head gasket repairs will cost less if you catch leaks early
The cost of repairing the head gasket ultimately depends on the speed at which the problem is detected. The longer you wait before going to the repair shop, the more you can expect to get back on the road.
Which workshop you choose naturally also affects how much you are likely to pay. While there shouldn’t be too much of a difference in the prices you’re offered, it is probably worth getting a few quotes from local mechanics so you can be sure you’re getting the best deal.