TEST 4: Using A Chemical Block Tester (Combustion Leak Tester)
In some cases, the head gasket failure does not cause the engine oil to mix with coolant, it doesn't cause the combustion pressures to escape into the radiator, and it doesn't cause the engine to misfire.
Usually, in these cases, the engine starts and runs but overheats within minutes.
The only way to pinpoint the overheating issue to a blown head gasket is performing a block test with a combustion leak detector.
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 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.
You can shop for a block tester here:
If this info really saved the day, buy me a beer!