Blown Head Gasket Tests (2002-2004 4.2L Oldsmobile Bravada, 2004-2007 4.2L Buick Rainier)

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

A head gasket failure can cause the engine to overheat (for no apparent reason) although the failure is not causing any of the symptoms the previous three tests check for.

The only way to pinpoint the engine overheating problem to a head gasket failure is by performing a block test with a block tester.

If you've never heard of a block test, the test uses a combustion leak detector tester to see if combustion/exhaust gases are escaping into the engine's 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 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 4.2L Oldsmobile Bravada And Buick Rainier Tutorials

You can find a complete list of 4.2L Oldsmobile Bravada and Buick Rainier tutorials and wiring diagrams here:

• GM 4.2L Index of Articles.

Here's a list of articles you'll find there:

• Electronic Throttle Body Tests (2002-2004 4.2L Oldsmobile Bravada, 2004-2007 4.2L Buick Rainier).
• How To Test Engine Compression (2002-2004 4.2L Oldsmobile Bravada, 2004-2007 4.2L Buick Rainier).
• TAC System Wiring Diagram (2002-2004 4.2L Oldsmobile Bravada, 2004-2005 4.2L Buick Rainier).
• How To Test The Ignition Coils (2002-2004 4.2L Oldsmobile Bravada, 2004-2007 4.2L Buick Rainier) .