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TEST 4: Using A Chemical Block Tester (Combustion Leak Tester)
In some cases, the head gasket fails in such a way that it cannot be diagnosed with any of the previous three tests. To be a bit more specific, even though the head gasket has failed:
- The oil hasn't turned milky white (TEST 1).
- The coolant isn't being shot out forcefully from the radiator (TEST 2).
- The engine compression values are OK (TEST 3).
The one symptom that you're going to see is that the engine overheats as soon as it starts and for no apparent reason. These hard to diagnose cases, you'll need to perform a block test with a chemical block tester to determine if the head gasket is the culprit.
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:
If this info saved the day, buy me a beer!
