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What happens if my car’s head gasket blows?

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Updated 10 Oct 2019

Jason Unrau

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It’s one of the worst scenarios for any car owner: a blown head gasket.

Your car is frustratingly unreliable and there’s no way out except for a full-fledged repair.

How can you be sure that your car’s head gasket gave up the ghost, and what can you do about it?

What Does the Head Gasket Do?

More accurately called a cylinder head gasket, its purpose is rather simple: to keep the cooling system passages, engine oil galleys, and combustion chambers separated and sealed between the cylinder head and the engine block.

For most modern cars, the cylinder head gasket is made of stamped steel layers, sometimes with flexible seals around the galleys and passages.

Older cars might incorporate asbestos or graphite layers, but they’re not as durable.

Extreme temperatures from the combustion chamber can cause cylinder head gaskets to burn through.

When it happens, coolant can enter the engine oil, oil can get into the cooling system, or either one can leak into the combustion chamber.

Or, there could be an external leak too.

How Do You Know the Head Gasket is Bad?

  • A bad cylinder head gasket becomes rather prominent – you can’t help but know something is amiss. Symptoms can include one or more of the following:
  • Smelly blue smoke from the tailpipe. It’s a clear sign engine oil is being burned in the engine, although it could be another cause also.
  • White smoke from the exhaust. White smoke indicates engine coolant is entering the combustion chamber.
  • The engine runs rough. Either oil or coolant can foul the spark plugs, resulting in poor idle and acceleration and often accompanied by a Check Engine light.
  • Temperature warning. The temperature gauge could spike into the red zone and your engine is likely to overheat.
  • Either coolant or oil leaking. If it’s an external leak, it’s obvious from the fluid on the ground.

Can You Drive with a Blown Head Gasket?

It’s a serious matter if your head gasket is blown.

On short trips, the engine might not get hot enough for symptoms to show up.

But once the engine is warm, it could easily start spewing steam, run very rough, or stall.

If you pretend you don’t see the symptoms and don’t get it looked at, you’re asking for more trouble and more expensive repairs.

It will quickly progress to more complicated and expensive repairs including plugged cooling system components, scored internal engine parts, or even a seized engine.

What Does Head Gasket Replacement Cost?

The cost to replace a blown head gasket varies widely and depends on the make, model, and engine your car has, as well as the extent of the damage.

A basic cylinder head gasket repair begins at $1200 but can range in price beyond $3000.

If the engine is beyond repair, you may be looking at a complete engine replacement instead.

You can easily compare quotes for a head gasket replacement with AutoGuru.

It only takes a few clicks and you’ll get quotes from high quality local mechanics ASAP!

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Written By

Jason Unrau

Jason is a Canadian automotive content writer with a background in the auto service industry, but he’s been hooked on cars and mechanics since childhood.

One of his first cars was an ’80 Mazda RX-7 that’s sorely missed to this day. A ’68 Ford Torino GT, a ’66 Ford Country Squire Woodie station wagon, and a ’96 Suzuki GSX-R 750 have spent time in his fleet of cars, bikes, and trucks over the past two decades.

Jason’s pride and joy is under construction – a turbocharged ’88 Mazda RX-7 convertible. Also on his resume is CASCAR official certification.