You’ve heard the phrase before – a blown head gasket.
It just sounds bad, even if you have no idea what it means. Sounds expensive, too.
Unfortunately, it is bad and it can be costly. But the good thing is it’s repairable if caught early enough. And it’s preventable with regular maintenance and proper driving.
By the end of this article, you’ll know exactly what a blown head gasket means, why it happens and how to prevent it.
So let’s open the hood and have a look…
What a Head Gasket Is and Does
The head gasket is one of the most important parts of a car’s engine. It’s a thin metal gasket mounted between the cylinder head and engine block.
Its primary job is sealing off the combustion chamber so the engine can build the right amount of compression.
Gasoline and air enter the combustion chamber as catalysts to create power. Coolant circulates to keep engine components from getting too hot. Engine oilcirculates to lubricate moving parts and help them last longer.
The head gasket keeps oil and coolant from entering the engine’s cylinders between power strokes. It also keeps coolant and oil from mixing when the engine is off.
With its vital role in the engine, the head gasket is under constant stress. Sometimes the stress gets the best of it, causing it to fail.
Why a Head Gasket Fails
A head gasket fails because of things we can’t control. An example of this is normal wear and tear from thousands of driving miles.
Another example is poor design. Older engines have thinner metal gaskets that can’t tolerate constant temperature changes for a long time. Some engines weren’t designed well and are notorious for head gasket failures.
Other reasons for failure are from things we can control. One of them is overheating. When the engine runs at high temperatures for long periods of time, excess expansion of the engine block and cylinder head occurs.
Engine pre-ignition can also cause head gasket failure. This happens when combustion falls out of time allowing coolant and/or oil to enter the cylinders.
And when coolant and oil get into the engine cylinders bad things happen.
Top Indications Your Head Gasket Is Blown
You can see, hear and smell the signs of a blown head gasket. As the failure gets worse, more signs emerge.
These are all indications you have a blown head gasket.
Engine Oil Milkshake
When coolant and oil mix, the oil changes colors and gets frothy. Kind of like a latte or a milkshake. You’ll see this on the dipstick and the underside of the oil fill cap.
White Smoke From the Tailpipe
Antifreeze entering the engine cylinders turns to gaseous form and mixes with other exhaust gases. The result is a sweet-smelling, white smoke.
Water Coming From the Tailpipe
A small amount of condensation from the tailpipe is fine. All it means is the engine is not yet at operating temperature. A steady stream of water, even after the engine is warm is the first sign of a problem.
A gush of water, or water mixed with the white smoke we covered earlier, indicates a head gasket leak.
Coolant Leak From the Engine
A coolant leak is the surest sign of a problem. Milky oil, white smoke, and water are all indicators of an internal leak.
External coolant leaks occur, as well. Coolant leaks from between the cylinder head and engine block. It’ll happen below the exhaust or intake manifolds.
When the car’s not running, you may see the actual coolant. When the car is running, it looks like steam coming from the engine.
Bubbling Coolant in the Reservoir
Another internal leak indicator is the presence of gas bubbles in the coolant reservoir. When a hole develops between the head gasket’s cooling jacket and the combustion chamber, exhaust gas can be pushed into the cooling passage.
If the leak is large enough, it will look like bubbles in the coolant overflow bottle.
Excess heat is a cause of a blown head gasket but it’s also an indicator of it.
The engine runs hotter because coolant escapes into the oil, exhaust or outside the vehicle. Inefficient combustion and the radiator’s inability to cool the dirty coolant also play a role.
Rough Running Engine and Power Loss
Head gasket failures sometimes occur between two cylinders. This allows the compressed air and fuel mixture to escape from one cylinder to another. This change in compression is a called an engine misfire and results in a rough sounding engine and loss of power.
Fouled Spark Plugs
When coolant burns off in the combustion chamber, white deposits get left on the spark plugs. This isn’t the main indicator but it’s a signal you should look for other issues.
None of the above sound good for your engine. And ignoring these signs won’t make the problem go away.
An unaddressed head gasket failure is a critical issue that leads to bigger problems.
What Happens if it’s Not Fixed
Coolant and oil weren’t meant to mix together. Neither was coolant and exhaust gases. The longer they stay together, the worse it is for your engine.
The longer coolant stays mixed with engine oil, the worse it becomes for the oil. First, the oil loses its viscosity or thickness. Second, because it’s thinner, its ability to lubricate engine parts diminishes.
Finally, important engine parts erode because of prolonged exposure to the coolant. The cylinder walls start to wear down, along with the crankshaft and camshaft bearings. Machined surfaces begin rusting, putting tiny pits in the metal.
Catalytic Converter Damage
When coolant leaks into the exhaust system, water and/or white smoke come out of the tailpipe. This means the coolant has already passed through the catalytic converter.
Over time, coolant clogs the catalytic converter and contaminates the materials inside.
Warped Cylinder Head and/or Engine Block
As we discussed before, overheating is a common cause and by-product of head gasket damage. Overheating, over a long period of time, does serious damage to your engine.
The cylinder head’s metal can warp. This happens more on newer vehicles with aluminum heads. A warped head can’t completely seal to the engine block.
The engine block can also warp with prolonged heat exposure. Sometimes both parts can be resurfaced by machining. But if the damage is too severe, replacement may be the only option.
Overheating is a problem that feeds on itself. It can cause head gasket failure and create even more damage afterward.
Proper maintenance, however, helps limit overheating and keep your engine running a long time.
Head Gasket Maintenance
The most important thing you can do for the health of your automobile is to follow the manufacturer’s maintenance schedule. It has what maintenance you need and at what intervals.
For your head gasket specifically, pay close attention to your cooling system. Do you smell coolant? Is the temperature gauge higher than normal?
Does the fan turn on when it’s supposed to? Are all the blades intact? Is the fan shroud cracked?
Check the coolant level periodically. Make sure coolant is at the proper fill level. Only use coolant that comes pre-mixed with water.
If your engine overheats, pull over and shut down the vehicle. Let it cool for an hour. Make sure the coolant is at the minimum mark, at least, before you resume driving.
Keeping engine RPM’s low will reduce the heat stress on your head gasket. For turbocharged vehicles, keep the boost level at the factory setting. This keeps combustion pressures at the proper level.
Sometimes maintenance isn’t enough, and the symptoms of a blown head gasket rear their ugly heads. Now what?
What to Do If Your Head Gasket Is Blown
If your car is drivable, have more than one mechanic diagnose the problem. Some of the symptoms mentioned earlier point to problems other than a head gasket failure.
If it is a blown head gasket, how extensive is the damage?
The best case scenario is only needing the head gasket replaced. Unfortunately, many times the problem isn’t found until more damage has occurred.
If the heads aren’t warped too badly, machining the surface fixes them. If they’re warped past repair, the engine will need to be rebuilt or replaced.
The most expensive option is replacement with a brand new engine. Remanufactured engines are available at significant cost savings. Used engines are also a good option and less expensive than remanufactured.
Once you know your options, you must decide if repairing the vehicle makes sense. What are the repair costs versus the cost of buying another vehicle?
With newer vehicles, the decision to repair may be a no-brainer. With older cars that are bound to have more problems, cutting your losses could be the right move.
Know it’s ok to walk away. We’ll give you an instant online offer for your vehicle and tow it away free of charge.