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Blown Head Gasket? What Is It?

by Eddie Carrara

You think you have a blown head gasket, so you bring it to your to your mechanic because the engine is not running right, or the temperature gauge is getting too high, the service advisor tells you to drop off the vehicle, and they will call you later with the diagnosis. 4 hours later, the advisor calls and tells you that the engine has a blown head gasket and it's going to cost you almost $3000 to fix it.  

To make matters worse, you may need some additional work because your engine overheated and the cylinder head may be warped, so you may also need some machine work done to the head, that would be an additional $300, then they ask, "would you like us to start on it today?"  At this point, your head is spinning because you don't even know what a head gasket is, or what is does!

After reading this article, you will know what a head gasket is, what it looks like, what its purpose is, and what the symptoms of a blown head gasket are.  If you still have question, you can place them in the comment box below and ship them off to me, I should be able to answer any questions you have, just so long that it isn't too technical, we keep it simple here.

A cooling system pressure tester can help diagnose leaks quickly, not only that, your engine can be cold when performing a pressure test, preventing you from getting burned by hot coolant.

So, What is a Head Gasket?

An engine is broken up into two parts, a cylinder block and a cylinder head. The block is where the pistons and cylinders are located, and the head is where the valves and rocker arms reside. In between where the head and the block meet, is where the head gasket is located.

The gasket is placed there so that in the event of a mechanical breakdown, the cylinder block and the head can be separated and repaired individually. The head gaskets only job is to seal the area where the two pieces of the engine meet.

The head gasket has to seal three areas between the cylinder block and the head. Here are the three areas the gasket seals:

1.       The combustion chamber, this is the area where the fuel, air, spark, and compression take place, the gasket needs to be able to withstand extreme temperatures and pressure in this area, so this is the most common place to have a head gasket failure, or a blown head gasket.

2.       The head gasket also seals the coolant passages between the cylinder block and head, there is not a whole lot of pressure in this area, but sometimes engine coolant can become corrosive due to the lack of service, and at this point, the coolant can eat away at the head gasket, and eventually it will cause a leak.

3.       The last area the head gasket seals is the oil passages, and again, there is not a lot of pressure in this area. It's rare to have a head gasket leak in this area, if it does, the most common cause is an inferior product or head gasket. In other words, the head gasket must have been defective straight from the manufacturer. 



What is a Symptom of a Blown Head Gasket?

Some might think the most common symptom of a blown head gasket is thick white smoke bellowing out the exhaust tail pipe, but it's not! The most common symptoms of a blown head gasket are:

  • Engine overheating or exhaust gases in the radiator.  If you think you may have exhaust gases in the radiator, the gases would be accommodated by constant bubbling in the radiator. 
  • Engine running poorly (skipping, hesitating, or lack of power).
  • Coolant in the oil which would cause your engine oil to become milky, and would have a very similar look to it like chocolate milk.
  • Excessive pressure in the crank case causing extreme blow by out the oil cap or engine oil seals. 

Head Gasket Test Kit

If the head gasket is blown out completely between the coolant passage and combustion chamber, the cooling system will build up extreme pressure and possibly blow off the radiator cap, crack the radiator tank, or blow a radiator hose, whichever is the weakest part of the cooling system, it will fail first.

Blown Head Gasket Sealers or Quick Fixes

If you're looking for a quick fix for a blown head gasket, stop!  There is no such product on the market, so if you're thinking about using quick silver power, or bars leak, it's only a temporary fix and could cause more problems down the road like:

  •  blockages in a coolant passage
  • clogged radiator tubes
  •  blockage in the heater core

You can take your chances with a head gasket sealer in an emergency, but in my personal opinion, you're flirting with disaster!  The quick fix may work for a week or two, but you'll pay handsomely in the end.

Thick White Smoke Coming From the Exhaust

If your problem is thick white smoke coming out the exhaust pipe, most likely you have a blown intake manifold gasket.  The reason it's not a blown head gasket is because head gaskets holds in pressure, therefore when a head gasket lets go, it releases pressure into the engine or causes coolant to leak into the oil passages. When an intake manifold gasket blows, it sucks coolant into the intake manifold and sends it straight into the combustion chamber causing the coolant to burn and cause a thick white smoke out the exhaust pipe, but we can save the rest of this conversation for another article.


In the video above, the engine was overfilled with oil, but a blown intake manifold gasket would have the same amount of smoke coming out the exhaust, the only difference would be that the smoke would be caused by burning coolant, not oil.

Still Not Sure You Have A Blown Head Gasket?

If you're still confused or if you have any questions, just leave them in the comment box below and I'll answer them as soon as I'm done setting the torque on these head bolts :)


If you know someone who could use the information on this page, just click this link, What Is A Blown Head Gasket? and send it to them in an email, share it on Facebook or post it on Twitter, thanks.

More Automotive Articles by Eddie Carrara

http://hubpages.com/hub/6-Most-Common-Fluid-Leaks-from-a-Car

http://hubpages.com/hub/4-Common-Car-Noises

http://eddiecarrara.hubpages.com/hub/Oil-Drain-Bolt-Repair



Click here to download your copy of my eBook, "Simple Car Care Tips and Advice" It's filled with usefull, easy to understand, automotive information you can really use!


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Eddie Carrara 

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