How To Test For A Blown Head Gasket (2000-2006 1.8L Nissan Sentra)

TEST 4: Using A Chemical Block Tester (Combustion Leak Tester)

Block Tester To Check For A Blown Head Gasket. How To Test A Blown Head Gasket (2000, 2001, 2002, 2003, 2004, 2005, 2006 1.8L Nissan Sentra)

Using a block tester to check for a blown head gasket when the previous 3 tests have not confirmed it will tell you without a doubt whether it's blown or not.

Why didn't I start with this test? Because TEST 1, TEST 2 and TEST 3 usually detect a blown head gasket about 95% of the time (not to mention you don't have to spend money on them). It's the remaining hard-to-diagnose 5% percent that are worth the effort to find a block tester.

In a nutshell, this is how a block tester works:

  • A blue liquid chemical, which is blue in color, is placed in the tester (see photo above).
  • The tester assembly is then placed on the open radiator neck (you may have to drain some of the coolant in the radiator since this tool needs to 'gulp' some of the air inside the radiator).
  • The engine is started.
  • The rubber bellow is then squeezed to suck in the air up through the two fluid-filled chambers. As the air bubbles up through the fluid, it will cause a chemical reaction.
  • If the blue chemical turns yellow (for gasoline engines), combustion gases are entering the radiator. This result confirms a head gasket failure, a cracked block, or a cracked cylinder head issue.
  • If the blue chemical doesn't change color, you can conclude that you don't have a head gasket failure, a cracked block, or a cracked cylinder head issue.

Where can you get the chemical and block tester? At your local auto parts store or here:

More 1.8L Nissan Sentra Tutorials

You can find more 1.8L Nissan Sentra tutorials in this index:

Here's a small sample of the tutorials you'll find in the index:

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Nissan Vehicles:

  • Sentra 1.8L
    • 2000,