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Head gasket replacement

Nearly all modern engines have a separate engine block and head assembly. Despite not being connected, they have to be bolted together to house the valvetrain, camshaft, and manage air coming in and exhaust going out. The fluids that keep the camshaft and valves lubricated and cooled aren’t meant to get into the combustion chamber.

What is a head gasket? 

A head gasket is a steel or composite material that is fitted between the head and cylinder block. This keeps the coolant and oil that are pumped through the head, not interfering with the engine’s operation.

When the head is bolted to the engine block, this creates an airtight seal. This seal keeps all the unwanted fluids out of the combustion chamber and keeps all the compression in the engine - making your engine more efficient.

Why do you need a head gasket?

Without a head gasket, unwanted oil can get into the cylinders which can damage spark plugs, oxygen sensors and really harm your fuel economy. Not to mention that if unnoticed, you could run your engine with not enough oil.

If coolant gets into the cylinders this can lead to your performance being far worse, water and fire don’t mix. Not to mention that the coolant can dilute the oil and ruin the bearings, spark plugs and pistons. Expensive repairs for a cheap part. 

How to tell if you need a new head gasket

The most tried and true way to tell if you need a new head gasket is white steam coming from the exhaust while running. If your oil is milky then it means that water is present in the oil. You can also tell from the coolant level slowly going down over time. 

If the engine is running poorly, misfiring or stumbling then it may be the head gasket to blame.

How is a head gasket replaced?

The mechanic will start by draining the oil and coolant from the engine. They will then unbolt everything attached to the head gasket (quite a lot of things in modern cars). They will then unbolt the cylinder head and remove it from the engine. While the heads are being cleaned the mechanic will lift the old head gasket off and scrape off any residue.

Once the surface is clean and level, the mechanic will fit the new head gasket with any sealant in required areas. The heads will be refitted and torqued to spec. All components will be reattached and the oil and coolant refilled.

After all that ordeal they will bring the engine up to running temperature and you’ll be good to go.

How much does a head gasket replacement cost? 

They aren’t cheap, the gaskets themselves are fairly inexpensive. Nearly all of the cost comes from the labour. 

It’s a long and arduous process to replace head gaskets. As a result expect prices to start from $1500 for a simple, straightforward job. That quickly climbs to over $3200 for more complicated head assemblies.

Luckily, head gaskets don’t have a habit of failing often, when they do - get it fixed immediately.

Is a broken head gasket unsafe?

It is extremely unsafe to your engine. If it leads to overheating this can warp the engine block and cause irreversible damage to the engine. Rather than do that, find a good mechanic who can fix it as soon as you notice the symptoms cropping up.

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