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

Block Tester To Check For A Blown Head Gasket

There are times when the previous three tests cannot pinpoint for a certainty that the head gasket is blown, yet your car continues to overheat for no apparent reason. In a case like this, the only way to make sure that the head gasket is not blown (or not) is by doing a block test.

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

  1. A blue liquid chemical, which is blue in color, is placed in the tester (see photo above).
  2. 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).
  3. 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.
  4. If the blue chemical turns yellow (for gasoline engines), then combustion gases are entering the radiator thus confirming a head gasket, a cracked blocked, or cracked cylinder head issue.
  5. If the blue chemical doesn't change color, then you can conclude that you don't a head gasket, a cracked blocked, or cracked cylinder head issue.

You can buy one here:

More 2.4L Diagnostic Tutorials

There are several more ‘how to’ tutorials that I've written that are 2.4L Quad 4 specific, that may be of further help. You can find the ones that are located here, at this site, by going to the GM 2.4L Index Of Articles.

The following is a sample of the articles you'll find in the index:

  1. How To Test The MAP Sensor (GM 2.4L Quad 4).
  2. How To Test The Starter Motor (GM 2.4L Quad 4).
  3. How To Test The Fuel Injectors (GM 2.4L Quad 4).
  4. How To Test The Ignition Module & Crank Sensor (GM 2.4L) (at:easyautodiagnostics.com).
Thank You For Your Donation

If this info saved the day, buy me a beer!

If This Info Saved the Day, Buy Me a Beer!


Buick Vehicles:

  • Skylark 2.3L, 2.4L
    • 1994, 1995, 1996, 1997, 1998

Chevrolet Vehicles:

  • Cavalier 2.3L, 2.4L
    • 1995, 1996, 1997, 1998, 1999, 2000, 2001, 2002
  • Malibu 2.4L
    • 1997, 1998, 1999

Oldsmobile Vehicles:

  • Achieva 2.3L, 2.4L
    • 1994, 1995, 1996, 1997, 1998
  • Alero 2.4L
    • 1999, 2000, 2001

Pontiac Vehicles:

  • Grand Am 2.3L, 2.4L
    • 1994, 1995, 1996, 1997, 1998, 1999, 2000, 2001
  • Sunfire 2.4L
    • 1996, 1997, 1998, 1999, 2000, 2001, 2002