How To Test A Blown Head Gasket (2004-2010 3.5L V6 GM Engine)

By: Abraham Torres-Arredondo
Created: 18 July 2018
Updated: 19 March 2024
Articl Id: 839

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

Using A Chemical Block Tester (Combustion Leak Tester). Testing For A Blown Head Gasket On The 2004, 2005, 2006, 2007, And 2008 3.5L Chevrolet Malibu

This is probably the most popular test performed at a repair shop to confirm or exonerate a blown head gasket problem.

I have performed this test many times to diagnose a hard-to-diagnose blown head gasket problem.

To be a bit more specific, there are some cases where the vehicle passes all of the previous tests and yet the engine seems to overheat for no apparent reason.

This is where a chemical block test will come in handy because it will give you a definite and conclusive answer as to whether the problem is being caused by a blown head gasket or not.

You can buy a block tester in just about any auto parts store. 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 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), then combustion gases are entering the radiator. This result confirms a blown head gasket, a cracked block, or a cracked cylinder head issue.
If the blue chemical doesn't change color, then you can conclude that you don't have a blown head gasket, 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: