Page 3 of 3
TEST 4: Using A Chemical Block Tester (Combustion Leak Tester)
Some head gasket failures do not cause any of the symptoms that the previous tests were trying to confirm.
In other words, the engine oil isn't mixed with coolant, the coolant does not get blown out of the opened radiator, and compression is good across all of the cylinders.
And yet the head gasket has failed and causes the engine to overheat, while it's running, for no apparent reason.
In these cases a 'block' test is required to pinpoint the problem to the head gasket.
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 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? At your local auto parts store or here:
20%$10.40
If this info saved the day, buy me a beer!
