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

Using A Chemical Block Tester (Combustion Leak Tester). How To Test For A Blown Head Gasket (2.3L Ranger, Mustang, B2300)

Every now and then, a blown head gasket problem doesn't show any of the symptoms the prior 3 tests are checking for. Yet your Isuzu continues to overheat. In these tough to diagnose cases, the only way to confirm (or disconfirm) a blown head gasket is by doing a block test with a chemical block tester.

The combustion leak tester (or block tester) test is so effective that it's used in all major/competent repair shops to confirm a blown head gasket issue. In a nutshell this is how the test works:

  1. A blue liquid chemical, which is blue in color, is placed in the tester (see photo above).
  2. 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).
  3. 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.
  4. 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.
  5. 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? Here:

Frequently Asked Questions

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

To find out if the cylinder head is cracked, it has to be off of the engine block and visually inspected and/or pressure tested.

If the crack is wide enough on the cylinder head, you'll be able to easily see it without having to have anyone check it.

If no cracks are visible to the naked eye, you still need to let a Machine Shop check it for you to make sure.

2.)  How can I find out if the cylinder head is warped?

The cylinder head has to be removed from the engine to find out.

Once out, the head gasket surface of the cylinder head has to be perfectly clean. A Precision Straight-Edge Tool (along with Feeler Gauges) is then used to accurately measure the warpage.

Now, if your vehicle overheated and the head gasket is blown, you can bet that the cylinder head is warped and will need to be resurfaced by a Machine Shop.

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

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

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Ford Vehicles:

  • Mustang 2.3L
    • 1991, 1992, 1993
  • Ranger 2.3L
    • 1989, 1990, 1991, 1992, 1993,1994, 1995, 1996, 1997, 1998

Mazda Vehicles:

  • B2300 2.3L
    • 1994, 1995