How To Test A Blown Head Gasket (3.1L V6 Buick, Oldsmobile)

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

I've run into some head gasket failures that did not present any of the symptoms that the previous 3 tests are designed to look for.

Specifically, the vehicle had a head gasket failure but the oil wasn't mixed with coolant, the coolant remained undisturbed in the radiator as the engine was cranked, and all cylinders had good compression.

Yet as soon as the vehicle was started, it would start to overheat. In these cases, the only way to pinpoint the problem to a blown head gasket is by doing a combustion leak detector test (commonly known as a block test).

This is how the combustion leak detector test (block test) works:

• The combustion leak detector tester is filled with a blue liquid chemical (see photo above).
• The radiator cap is removed (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 tester is then placed on the open radiator neck.
• 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 in turn 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 cracked cylinder head issue.

You can shop for a block tester here:

More 3.1L V6 Buick, Oldsmobile Tutorials

You can find a complete list of 3.1L V6 Buick (Oldsmobile) tutorials in this index:

• GM 3.1L Index Of Articles.

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

• How To Test Engine Compression Test (3.1L V6 Buick, Oldsmobile).
• How To Test The MAP Sensor (3.1L V6 Buick, Oldsmobile).
• How To Test The Fuel Pump (3.1L V6 Buick, Oldsmobile).
• How To Test The 24X Crankshaft Position Sensor (1995-1997 3.1L V6 Oldsmobile Cutlass Supreme).