How To Test A Blown Head Gasket (3.1L V6 Chevrolet And Pontiac Vehicles)

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

Every now and then, you'll have a case where the engine has a blown head gasket issue but you're not going to see the coolant mixed with oil, you're not going to see the coolant being shot out of the radiator, and you're not going to see any compression problems.

Yet the engine overheats as soon as it starts due to a head gasket failure. The only way to find out if the overheating issue is due to a blown head gasket is by doing a block test with a combustion leak detector tool.

A block test simply involves using a chemical combustion leak detector tool that checks to see if combustion gases are leaking into the engine cooling system.

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), then combustion gases are entering the radiator. This 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 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:

More 3.1L Chevrolet (Pontiac) Tutorials

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• GM 3.1L Index Of Articles.