How To Test For A Blown Head Gasket (2003-2013 V8 Chevy Express, GMC Savana)

TEST 3: Engine Compression Test

As you're probably already aware, a head gasket acts as a seal between the cylinders, ensuring that each cylinder maintains proper compression for combustion.

If the gasket fails in a region between two side-by-side cylinders, it compromises the seal, allowing compression gases to leak across and equalize pressure. As a result, both cylinders may experience a loss of compression, leading to 0 PSI readings when tested (the head gasket in the photo at the start of this tutorial exemplifies this type of failure).

While this type of head gasket failure doesn't happen every day, it's common enough that we need to check for it. You can easily do this by doing an engine compression test and in this section, I'll walk you through the compression test.

NOTE: You can find the engine compression test and how to interpret its results explained in more detail here: How To Do A Compression Test (2003-2014 V8 Chevrolet Express, GMC Savana).

OK, these are the test steps:

1. 1

   Disconnect the ignition coils from their electrical connectors. This is will disable the ignition system and is an important safety precaution.

2. 2

   Disconnect all spark plug wires (from their spark plugs).

3. 3

   Remove all of the spark plugs.

4. 4

   Thread in the compression tester by hand, on the first spark plug hole you're gonna' start with.
   
   Do not use any tools to tighten the compression tester. Hand tightening the compression tester is more than enough to get the proper results.

5. 5

   Have a helper crank the engine as you observe the compression tester.

6. 6

   When the gauge's needle stops climbing, have your assistant stop cranking the engine.

7. 7

   Write down the reading and what cylinder it belongs to on a piece of paper (you can use the illustration above to help you identify the cylinder).

8. 8

   Remove the compression tester and repeat the above steps in the remaining cylinders.

Let's examine what your results mean:

CASE 1: All cylinder compression readings where normal. This is the correct test result and it confirms that the head gasket isn't burned at a spot between two side-by-side cylinders.

If you still suspect a blown head gasket, go to: TEST 4: Using A Chemical Block Tester (Combustion Leak Tester).

CASE 2: Two side by side cylinders had 0 PSI compression. This test result confirms that the head gasket is burned at the point between those two cylinders. Replace the head gasket.

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

While oil mixing with coolant and compression gases escaping into the engine's cooling system are common symptoms of a blown head gasket, there are situations where these signs may not be present. In such cases, diagnosing a head gasket issue accurately can be challenging.

One effective method for diagnosing a head gasket issue, particularly when traditional symptoms are absent, is to perform a block test using a combustion leak detector. Here's how it works:

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 Chevy Express/GMC Savana Articles And Tutorials

You can find a complete list of articles and diagnostic tutorials for the V8 Chevy Express and GMC Savana here:

• GM 4.8L, 5.3L, 6.0L Index of Articles

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

• How To Test For The Fuel Pump (2008-2013 V8 Chevy Express, GMC Savana).
• How To Test The CKP Sensor (2008-2013 Chevrolet Express, GMC Savana).
• How To Diagnose An Engine Cranks But Does Not Start Problem (2003-2007 V8 Chevy Express, GMC Savana).
• How Can I Tell If The Automatic Transmission Is Bad? (2003-2013 Chevrolet Express, GMC Savana).