How Do I Know if I Have a Blown Head Gasket? (And What Does It Sound Like?)

You may not know much about it, but you will most likely dread the concept of a blown head gasket regardless. This is completely understandable - particularly if this fear is accompanied by a new noise emanating from your car. 

Read on and find out what a blown head gasket actually is, and how to listen out for one. 

What Is a Blown Head Gasket?

A ‘blown head gasket’ is what happens when the seal between the engine block and cylinder head wears away. The previously sealed coolant and oil return passages may be impacted as a result, and these liquids may leak into the cylinders. This is usually caused by an overheating engine, as the increase in thermal pressure will put additional strain on your car’s head gasket. 

It could also be the result of issues with the coolant or cooling system. Some vehicles will have a coolant level warning light which can indicate that there is a problem with the head gasket. Alternatively, it could be related to problems with pre-ignition, which can in turn cause a fuel leak if combustion does not happen when it is supposed to.

A blown head gasket is never a good sign - and definitely something worth getting checked out by a professional mechanic.

What Are The Most Obvious Signs of a Blown Head Gasket?

If your vehicle is experiencing a blown head gasket, then there are several telltale signs to look out for which can bring this to your attention.

Possible indications of a blown head gasket include:

• White exhaust smoke
• Loss of coolant - with no obvious leaks
• Milky white oil
• Bubbling in the coolant reservoir or radiator
• Engine gauge shows maximum temperature (quickly)
• Overheating engine

Whether you notice fluid leaking from your engine, smoke billowing from your exhaust, or a sweet smell in the air, your vehicle will offer plenty of warning signs. 

You may also notice a loss of engine power, as the pressure in the combustion chamber decreases. If you suspect that your engine is overheating, stop driving immediately and call a mechanic to help you. It may interest you to know that just as an overheating engine can cause head gasket failure, head gasket failure can lead to the engine overheating - so both issues should be taken seriously. 

Milky white oil in the filler cap is likely the result of oil mixing with coolant. If your engine oil is contaminated, it won't be able to keep the engine running safely, so you will need a head gasket replacement - and soon! Even though milky white oil is not a definite sign of a blown head gasket, the engine still needs to be looked at by a mechanic.

At the first instance of any of these issues, you should have your car looked at by a professional garage - you may just prevent the need for a costly head gasket replacement. 

What Sound Does a Blown Head Gasket Make?

Due to the fact that the combustion chamber is improperly sealed, the combustion of fuel and air will be limited. You may notice that the performance of your vehicle has worsened, and may even be able to hear an exhaust leak or rough idling noise - a clear indication of a blown head gasket.

When your head gasket fails, the pressure within the cylinders will not be at the correct level. This can explain the poor performance and rough idling noise. Though, a rough idling noise is not always related exclusively to a blown head gasket. You should not ignore a rough idling noise, and have your car checked out by a mechanic as soon as you can. 

You may even hear a knocking sound emanating from the engine, or the sound of a misfire, depending on how the head gasket blew. The sound of a misfire could be related to an overheating engine, coolant leak, or lowered compression as a result of rough idling. You are likely to hear a misfire during ignition if your car has a head gasket failure, particularly when you restart the car.

What Happens If You Don't Fix a Blown Head Gasket?

Whilst it can be frustrating to think about the potential repair costs, if you neglect to do something about a blown head gasket, then this could cause further damage to your vehicle. Better to do something about the problem sooner, than deal with additional repairs that a prolonged issue could cause. 

The coolant leaks that result from a blown head gasket can:

• Damage the engine/lubrication system
• Damage the catalytic converter
• Cause the engine to overheat

An overheating engine can result in further damage to the cooling system, radiator, and hoses. To stay safe, you need to do something about your blown head gasket as soon as you suspect there is an issue.  

At the same time, it is worth bearing in mind that these symptoms - namely coolant leaks and an overheating engine - could be related to another component entirely, such as the intake gasket or radiator. The only way to know for certain is to trust a professional mechanic to take a look and diagnose the problem for you.

Is It Safe To Drive With a Blown Head Gasket?

You should avoid driving with a blown head gasket, as your engine will have less power and could overheat and cause real damage to your car. Do not drive your car to a garage. Call a mechanic and have the car towed instead, and do this sooner rather than later before the problem worsens.

Remember to top up your coolant levels as needed to prevent head gasket failure from occuring in the first place.

If you suspect that your vehicle may have suffered from a blown head gasket, then now is the time to book a repair and get the problem sorted. You can have your car’s head gasket checked out by a professional mechanic and prevent future problems from arising when you book a visual inspection through BookMyGarage.