What Is a Blown Head Gasket?

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What Is a Blown Head Gasket?
There is hope for your head gasket ("Audi A6 2.5 TDI - Water pump replacement" is Copyrighted by Flickr user: whiskymac (Reg Mckenna) under the Creative Commons Attribution license.)

A head gasket is the part of an internal combustion engine that seals the cylinder head to the engine block. The purpose of this component is to make sure that the compression stays at a maximum level and the coolant or engine oil doesn't leak into the cylinders. However, head gaskets have been known to fail quite commonly. Severe damage to the head gasket that causes it to completely break down is known as a blown head gasket.

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Expert Insight

When a head gasket fails, it usually happens at the thinnest area between adjacent cylinders, which is a weak point. The head gasket cracks or gets burnt, and as a result compression leaks between cylinders. This leads to a significant drop in engine power and performance.

Other problems can occur as well. For instance, exhaust gasses could find their way into the cooling system, and the coolant may leak into the cylinders. The result is that the engine overheats. Also, when the coolant leaks, it dilutes the motor oil, which increases engine wear. If coolant continues to leak into the cylinders, the engine might "hydrolock." The eventual result is significant engine damage.

Driving With a Blown Head Gasket

It may be possible to temporarily drive with a blown head gasket. However, if you continue to do so, it will continuously cause damage to the engine because of repeated overheating and a relentless loss of lubrication. Eventually, all the coolant will be gone and your engine will fail.

Why Does a Head Gasket Blow?

Several factors will cause your head gasket to blow. The use of aluminium cylinder heads instead of iron ones in some modern cars is one reason. Aluminium has a greater thermal expansion rate than iron, which places more stress on the head gasket and may cause it to fail.

Another common reason is improper installation of the head gasket. During repair or service, if the head bolts weren't torqued in the proper sequence or to the specified value, your head gasket may leak and eventually fail. In addition, engine overheating and abnormal combustion can cause head gasket failure.

The Cost of Repair

When it comes to a blown head gasket, repair essentially means replacement. Provided you do get it repaired with the dealer or a reliable independent repair shop with decent parts, be prepared for a cost ranging between £650 and £1,950. According to RepairPal's Repair Price Estimator, the cost to repair a blown head gasket on a 2004 Toyota Camry will cost you approximately £711 to £921 for repair. How expensive the repair is depends on where you get it replaced, the make and model of your car, the type of engine and the quality of parts that are being used.

Doing it Yourself

You can repair this problem yourself at a fraction of that cost. Even though the process is not difficult, it is very time consuming and requires at least some skill with mechanical repairs. If you can handle the basics and time is not a problem for you, you'll be able to do it, and save yourself £520 to £650 in the process.

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