How do I know if my Head Gasket is blown? Using a pressure tester to determine if you have a blown head gasket

0643C827A7A7EB865AB79EFD8B49A2DAB2DFF5FA_smallDetermining whether or not your vehicle has a blown head gasket, cracked head, or some other serious engine problem can sometimes be a difficult task.  A compression test can tell you that cylinders are low but don’t always indicate what the problem is and can lead to wasted money. This article will discuss a method on how to test for a cracked head or blown head gasket.  This method is extremely simple and can be accomplished in several minutes with the right tools. To understand how this method works we will have to discuss how your engine’s cooling system works.  Your engine’s cooling system works by flowing coolant through a radiator and allowing air to pass through thus cooling the coolant.  The coolant then travels through a hose to the engine block.  The engine block has many coolant passages that flow through it.  These passages flow through the block itself and through the heads. If you have a blown head gasket or cracked head, you will end up having several situations occur.  The first is that you can end up burning coolant in your engine.  This is not good and can lead to premature bearing failure.  When engine oil and coolant mix the coolant displaces the oil and your engine lacks lubrication because in place of oil there is coolant.  Another thing that can occur when you burn coolant is that you can cause a severe overheat condition for your engine.  This can lead to piston’s reaching excessive temperatures and expanding and touching the cylinder walls.  This will cause scoring of the cylinders and pistons.  The last common problem that can occur is that combustion gases escape into your cooling system.  This can cause a decrease in power, and if in excess can cause cooling system problems. With all of these problems at risk and now that you understand how your engine’s cooling system works, we can now discuss the simple procedure to determine whether or not your engine in deed has a cracked head or blown head gasket.


The Procedure

  1. First you will want to park your vehicle.
  2. Make sure that your vehicle has not been driven in awhile.  This is extremely important.  You will have to remove the radiator cap and if you remove a radiator cap on a hot engine you can be scalded by burning hot coolant.
  3. With your cold engine remove your radiator cap.  Make sure to top off the fluid if the level is low.
  4. Replace your cap from your radiator with the correct cap from a coolant system pressure tester.  This AST7858 Radiator Pressure Tester has all the attachments for most vehicles.  Make sure that you use the correct size cap.
  5. With the pressure tester in place, you will want to connect the gauge from the pressure tester kit.
  6. Now that you have a pressure gauge in place you can now test to see if you are getting combustion gases leaking into your cooling system.
  7. To check you will have to start your vehicle.  Start your engine on your vehicle.
  8. Check the gauge.  It should read zero if you don’t have combustion gases leaking in. It may read a slight amount of pressure.  Since your engine is cold the thermostat will not be open so there should not be any pressure.
  9. If you have any pressure, or the gauge goes up quickly then you have combustion gases leaking into the coolant system.  It may take a little time for pressure to build up.  You may have to wait for the thermostat to open up.  With a proper system when the thermostat opens the pressure will build slowly.  If you have combustion gases leaking into the system once the thermostat opens the pressure will rise extremely fast.
  10. If any pressure is present, IMMEDIATELY SHUT OFF THE ENGINE.  This is important because your compression gases reach a much higher pressure than your radiator and cooling system are made for.  If you don’t shut off the engine, you risk damaging the tester, or worse damaging the cooling system which can lead to a much more costly fix.

To summarize, basically if you start the engine and the gauge goes up fast immediately you have a blown head gasket, cracked head, or some other leak of combustion gases into your cooling system. You just finished diagnosing whether or not your engine failure is something to do with your engine’s cooling system. Written by: Cody Mammenga an NDSCS Student

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