How To Test For A Blown Head Gasket (2001-2005 1.7L Honda Civic)

By: Abraham Torres-Arredondo
Created: 27 January 2014
Updated: 15 February 2024
Articl Id: 544

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

Using a block tester, to check for a blown head gasket when the previous 3 tests don't confirm it, will tell you without a shadow of doubt if it's blown or not.

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.

Where can you get the chemical and block tester? At your local auto parts store or here:

UView 560000 Combustion Leak Tester

OEMTOOLS 27145 Combustion Leak Detector, Plastic and Rubber Tester for Engine Block Leaks, Automotive Blown Head Gasket Test

Lisle 75630 Test Fluid

How To Test For A Blown Head Gasket (2001-2005 1.7L Honda Civic)

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

More Honda Civic Test Tutorials