How To Test A Blown Head Gasket (GM 3.1L, 3.4L)

  • By: Abraham Torres-Arredondo
  • Created: 30 March 2011
  • Updated: 13 February 2024
  • Articl Id: 327
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TEST 4: Using A Chemical Block Tester (Combustion Leak Tester)

Block Tester To Check For A Blown Head Gasket

In the tough to diagnose blown head gasket cases, the previous 3 tests will not confirm a blown head gasket. In these cases, the one test that will settle the matter in a definitive way is a block test with a combustion leak detector.

Why didn't I start of with this test? Because TEST 1, TEST 2, and TEST 3 usually pinpoint a blown head gasket condition in about 95% of the cases (not to mention you don't have to spend any $$ to do them). It's the remaining hard to diagnose 5% percent where the effort of finding a block tester is worth it.

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), 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 buy one here:

UView 560000 Combustion Leak Tester
UView 560000 Combustion Leak Tester
OEMTOOLS 27145 Combustion Leak Detector, Plastic and Rubber Tester for Engine Block Leaks, Automotive Blown Head Gasket Test
OEMTOOLS 27145 Combustion Leak Detector, Plastic and Rubber Tester for Engine Block Leaks, Automotive Blown Head Gasket Test
Lisle 75630 Test Fluid
Lisle 75630 Test Fluid

Related Test Articles

There are several more GM 3.1L, 3.4L specific ‘how to’ tutorials that I've written for your troubleshooting and diagnostic benefit. The articles that are here in this web site, you can find them here: GM 3.1L, 3.4L Index Of Articles.

The following articles are found at easyautodiagnostics.com, which is the other Web Site that I write for.

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  2. Applies To:

Buick Vehicles:

  • Century
    • 1996, 1997, 1998, 1999, 2000, 2001, 2002, 2003, 2004, 2005
  • Regal
    • 1994, 1995, 1996
  • Rendezvous
    • 2002, 2003, 2004, 2005
  • Skylark
    • 1994, 1995, 1996, 1997, 1998

Chevrolet Vehicles:

  • Impala
    • 2000, 2001, 2002, 2003, 2004, 2005
  • Lumina
    • 1995, 1996, 1997, 1998, 1999, 2000, 2001, 2002, 2003
  • Monte Carlo
    • 1995, 1996, 1997, 1998, 1999, 2000, 2001, 2002, 2003, 2004, 2005

Chevrolet Vehicles:

  • Venture
    • 1997, 1998, 1999, 2000, 2001, 2002, 2003, 2004, 2005

Oldsmobile Vehicles:

  • Achieva
    • 1994, 1995, 1996, 1997, 1998
  • Alero
    • 1999, 2000, 2001, 2002, 2003, 2004

Oldsmobile Vehicles:

  • Cutlass
    • 1997, 1998, 1999
  • Cutlass Ciera
    • 1996
  • Cutlass Supreme
    • 1994, 1995, 1996, 1997
  • Silhouette
    • 1996, 1997, 1998, 1999, 2000, 2001, 2002, 2003, 2004

Pontiac Vehicles:

  • Aztek
    • 2001, 2002, 2003, 2004, 2005
  • Grand Am
    • 1994, 1995, 1996, 1997, 1998, 1999, 2000, 2001, 2002, 2003, 2004, 2005
  • Grand Prix
    • 1994, 1995, 1996, 1997, 1998, 1999, 2000, 2001, 2002, 2003

Pontiac Vehicles:

  • Montana
    • 1999, 2000, 2001, 2002, 2003, 2004, 2005
  • Trans Sport
    • 1996, 1997, 1998