What are the symptoms of a Blown Head Gasket?

blown head gasket symptomsThere are some makes or models of cars that have a reputation for blowing head gaskets.  One such vehicle has such a bad reputation for head gasket problems there is a group of owners trying to get the manufacturer to have a recall on them.  If you happen to own one of these vehicles, don’t worry it does not mean that you have a bad car or that you are going to spend lots of money.

What is a Head Gasket?

head gasket, blown head gasket symptomsLet’s start by talking about what a head gasket is.  The head gasket lives between your engine block and cylinder head.  Every modern car has this gasket but they vary in their thickness and construction based on the manufacturer’s design of the engine.   The head gasket is so important because it seals the combustion chamber allowing your car to build the proper compression and contain exhaust gases both of which aid in maintaining the efficiency of your engine.  The head gasket also keeps coolant and oil out of the combustion chamber which is important for the same reasons you wouldn’t want coolant or oil leaking anywhere else.

Now that we understand what a head gasket it, it’s important to learn what blown head gasket symptoms look like to avoid higher expenses due to additional engine damage caused by driving with a blown head gasket.  To understand the symptoms it can be helpful to understand why a head gasket might fail.

Why Do Head Gaskets Blow?

The head gasket forms a seal between the engine block and the cylinder head.  This means your head gasket has to seal both extremely hot, high-pressure combustion gases as well as engine coolant which can be anywhere from cold ambient temperatures to the normal operating temperature of your engine.  Due to the wide range of temperatures and relatively large surface area, it is not unusual for head gaskets to develop leaks over time.  This can happen regardless of the make or model of your car or the type of head gasket used.  To better understand why a head gasket might blow, check out this article on why head gaskets blow.

Since the head gasket seals the coolant passage both from the atmosphere and the combustion chamber you can’t see much of the head gasket on a vehicle with the engine installed.  Because much of the gasket can’t be seen without disassembling the engine, blown head gaskets symptoms can be very difficult to diagnose.  Since a visual inspection usually will not prove a head gasket leak, it is important to know the other symptoms so you can accurately diagnose a head gasket problem.

How To Tell if a Head Gasket Is Blown:

  • Coolant leaking externally from below the exhaust manifold
  • White smoke from the exhaust pipe
  • Bubbles in the radiator or coolant overflow tank
  • Overheating engine
  • White milky oil
  • Fouled spark plugs
  • Low cooling system integrity

External Head Gasket Leak

A head gasket leaking external would cause coolant to come from below the intake or exhaust manifold and often only happens when the engine is completely warmed up.  If there are no other cooling passages or hoses near the head gasket you may be able to positively identify the leak as a head gasket leak, but if there are other cooling passages nearby, you may need to add a UV dye to the coolant  then watch the head gaskets with a UV light to positively identify the leak.

White Smoke From Tailpipe

Most head gasket leaks are internal to the engine allowing coolant to flow into the combustion chamber on every intake stroke.  When this happens to coolant burns/evaporates with the combustion process and appears as white smoke coming from the tailpipe.  This smoke can be differentiated from moisture during a cold start by a sweet smell and will continue even when the engine is warm.  If the leak in the head gasket is large this white smoke can often be excessive and billow from the tailpipe.

Bubbles in the Radiator

Besides allowing coolant into the combustion chamber, an internal head gasket leak allows exhaust gases into the coolant.  This can cause bubbles to be in the radiator or coolant reservoir making the coolant look like it’s boiling even when it’s cold.  The bubbles are exhaust gases that force their way into the cooling system during the combustion process.  An easy do-it-yourself test for a blown head gasket is to perform a chemical test using this type of tester on your coolant to check for the presence of exhaust gases to see if this is happening in your car.  This is the most effective blown head gasket test and can give you a positive sign of a blown head gasket.

Overheating Engine

If you’ve got a blown head gasket, your engine usually will overheat after longer drives.  This happens both due to the lack of coolant as your engine consumes it, but also the efficient combustion process, the excess heat from the exhaust in the coolant and the inability of your vehicle’s radiator to cool the dirty coolant.  If your engine overheats it can cause lots of problems.  The biggest concern is the expansion of metal components past what they were designed for which can cause cracks and warping.  Also, it can permanently damage seals and gaskets cause other leaks in your engine.  Both of these problems often require a full engine rebuild to remedy.

White or Milky Oil

As coolant leaks into your combustion chamber, it will seep past your piston rings into your oil.  Over time oil and water will mix and cause the oil to turn a milky white.  You can look for this on your dipstick and around your engine oil cap.  Having water in your oil will make your oil ineffective in properly lubricating your motor which will quickly allow wear on your cylinder walls and on the crank and camshaft bearings.  Even if you don’t drive the vehicle, the presence of water in the oil can cause rust on machined surfaces which can lead to pitting in the metal and necessitate and engine rebuild.

Fouled Spark Plug

As coolant burns in your combustion chamber, it will leave tiny white deposits on your spark plug usually around the ground strap and electrode.  Other problems can cause these white deposits so this isn’t a conclusive blown head gasket symptom but if others are present it could give you more proof. 

Low Cooling System Integrity

If there is a leak from your head gasket, pressurizing your cooling system and watching for pressure loss can help prove you have a blown head gasket as well.  Since there could be other leaks you don’t know about, this also isn’t a conclusive test, but again just more indications that you may have a blown head gasket.  Similarly, you can perform a leak down test which pressurizes the combustion chamber with compressed air and measured the amount of air that leaks out through the head gasket or any other opening the combustion chamber.

Can I Drive With a Blown Head Gasket?

If you have multiple blown head gasket symptoms, it is important to drive your vehicle as little as possible.  The hot gases and cold coolant moving through the hole in the gasket can quickly erode or warp the metal head or engine block leaving you with costly machining bills or even having to purchase new heads or a new engine and having water in your engine oil can destroy bearings quickly.

How do I Avoid Getting a Blown Head Gasket?

There are some ways you can reduce your chances of blowing a head gasket.  The first is to keep combustion chamber pressures as low as possible.  If your vehicle is turbocharged or supercharged, make sure your boost level is set to the factory setting to keep combustion pressures in check.  Also, make sure your engine doesn’t have any preignition or knocking from overly advanced timing or carbon build up.  Similarly, maintaining low engine RPMs will reduce stress and heat on your head gasket so avoid running your engine at high RPM.  Lastly, if your car has a manual transmission avoid downshifting to slow the car and rev-match anytime you can to reduce pressure on your head gasket.

If you are rebuilding an engine, you can reduce the risk of a blown head gasket in the future by using properly lubricated head studs torqued in the proper sequence to the correct torque setting.  You can also make sure your block deck and cylinder head mating surface are properly prepared for the new gasket.  Similarly, using a multi-layer steel or other metal head gasket can improve the reliability of your engine.  For more information, check our complete article on how to prevent a blown head gasket

How Much does a Head Gasket Repair Cost?

Head gasket repair cost can vary significantly from vehicle to vehicle.  Cost factors include:

  • Number of cylinder banks
  • Overhead cam VS pushrod engines
  • Head or block damage
  • other components replaced

Most of the cost of a head gasket repair is in the labor costs so the complexity of the job can change the cost significantly.  For example, a “V” style engine has 2 heads and it is best to replace the gasket on both so the cost increases significantly over an inline engine.  Similarly, an engine with overhead cams adds the complexity of removing the timing belt or chain which makes the job more complicated than it would be on a pushrod engine where you simply need to remove the rockers and pushrods.  Machine work can add lots of cost to a head gasket job so knowing how much damage has been done to the head or block is important in calculating the cost of your head gasket repair.  Lastly, there are lots of other parts that can be replaced when repairing a head gasket like other gaskets and seals, belts, or the water pump and those parts costs can add up quickly as well.  For more information on calculating the head gasket repair costs for your car, check out our article on head gasket repair costs.

To quickly and permanently seal your blown head gasket, go to your local auto parts store and pick up one of BlueDevil’s head gasket sealing products.  If you have a small leak or 4 or 6 cylinder engine pick up BlueDevil Pour-N-Go 16oz Head Gasket Sealer.  Simply add it to your radiator and your head gasket leak will be sealed as your drive!  For larger leaks or 8 cylinder engines, use BlueDevil Head Gasket Sealer.  BlueDevil Head Gasket Sealer requires the removal of your vehicle’s thermostat and a complete cooling system flush but is guaranteed to fix your blown head gasket!

Don’t risk getting stranded or damaging your vehicle’s engine by driving with a blown head gasket.  Stop by your local auto part store today and pick up the quick and easy solution from BlueDevil!

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Pictures Provided By:

blown_head_gasket_symptoms.jpg – By Alex_Lshchenko – Licensed by Getty Images – Original Link
head_gasket.jpg – by Urfinguss – Licensed by Getty Images – Original Link