How To Test For A Blown Head Gasket (1988-1993 2.8L Chevrolet S10 Pickup, GMC S15 Pickup, GMC Sonoma)

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

If the previous three tests failed to detect a head gasket failure, cracked block, or cracked cylinder head issue in the engine, there is still a solution. A chemical block test can be performed to diagnose the problem.

The combustion leak test done with a block tester is the go-to test to confirm a head gasket failure in most (if not all) automotive repair shops.

NOTE: This test only works if the engine starts.

This is how it 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 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), then combustion gases are entering the radiator. This result 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 a cracked cylinder head issue.

Where can you get the chemical and block tester? You can buy here:

Frequently Asked Questions

1.)  How can I tell if the cylinder head is cracked?

The only way to know is to remove the cylinder head and visually inspect it. If the crack is wide enough, you'll be able to easily see it.

In many instances, a visual inspection won't be enough, you'll need to have the machine shop, that's gonna' resurface the cylinder head, for a pressure test.

2.)  Do I need to resurface the cylinder head?

The answer is YES! You should never reinstall the cylinder head or cylinder heads without first having a Machine Shop resurface the cylinders heads (particularly over an overheating condition).

Now, of course, if you (or the machine) have checked it with a straight-edge and there's no warpage, then, and only then is the cylinder head not resurfaced.

3.)  I have a V6, do I need to remove both cylinder heads?

It's standard practice to remove them both and replace both cylinder head gaskets (and have both cylinder heads resurfaced).

This is important because the only way to make sure the other cylinder head isn't extremely warped or cracked is by removing it and and visually inspecting it and taking the necessary warp measurements with a straight edge and doing a pressure test.

More 2.8L Chevy S10 Pickup, GMC S15 Pickup, And GMC Sonoma Tutorials

You can find a complete list of tutorials for the 2.8L V6 Chevrolet S10 pickup, GMC S15 pickup, and GMC Sonoma in this index:

• GM 2.8L Index Of Articles.

Here's a sample of the articles, you'll find in the Index of Articles:

• How To Test The Fuel Pump (1988-1993 2.8L Chevrolet S10 Pickup, GMC S15 Pickup, GMC Sonoma).
• How To Test Engine Compression (1988-1993 2.8L Chevrolet S10 Pickup, GMC S15 Pickup, GMC Sonoma).
• How To Test The EGR Valve (1988-1993 2.8L Chevrolet S10 Pickup, GMC S15 Pickup, GMC Sonoma).
• How To Test The Starter Motor (1988-1993 2.8L V6 Chevrolet S10 Pickup, GMC S15 Pickup).