How To Test For A Blown Head Gasket (3.9L Dodge Ram Pickup And Van)

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

A blown head gasket can cause the engine to overheat within minutes of it starting but it won't present any of the other symptoms the previous 3 tests were checking for.

The only way to confirm that the problem is being caused by a blown head gasket is by doing a block test with a block tester.

A block test is another name for a combustion leak detector test. And let me tell you, that a block test is the best way to find out if the head gasket is blown or not in those cases that the previous 3 tests cannot confirm or disprove a blown head gasket.

This is how this test 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 cranked and 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.

You can shop for a block tester here:

Related Test Articles

There are several more 3.9L V6 Dodge specific ‘how to’ tutorials that I've written for your troubleshooting and diagnostic benefit. To go there now, click here: Chrysler 3.9L Index Of Articles.