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

Block Tester To Check For A Blown Head Gasket

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 pin-point 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:

  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 thus confirming a head gasket, a cracked blocked, or cracked cylinder head issue.
  5. If the blue chemical doesn't change color, then you can conclude that you don't a head gasket, a cracked blocked, or cracked cylinder head issue.

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

Frequently Asked Questions

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

The cylinder head has to be removed and visually inspected. If the crack is wide enough, you'll be able to easily see it.

Sometimes, a visual inspection proves inconclusive, this is why it's important to let a machine shop pressure test it for you.

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

YES, you need to resurface the cylinder head! You should never reinstall the cylinder head or cylinder heads without first having a Machine Shop resurface the cylinders heads (particularly over an overheating condition).

Now, of course, if you (or the machine) have checked it with a straight-edge and there's no warpage, then and only then is the cylinder head not resurfaced.

More 1.6L Toyota Tutorials

There are several more ‘how to’ tutorials that I've written that are 1.6L Toyota specific, that may be of further help. You can find the ones that are located here, at this site, by going to the Toyota 1.6L Index Of Articles.

Here's a small sample of the tutorials you'll find in the index:

  1. How To Test The Front O2 Heater (1996-1997 1.6L Corolla).
  2. How To Test The Rear O2 Heater -P0141 (1996-1997 1.6L Corolla).
  3. How To Retrieve Toyota Corolla OBD I Trouble Codes.
  4. How To Test The Throttle Position Sensor (1.6L Toyota Corolla).
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Toyota Vehicles:

  • Corolla 1.6L
    • 1989, 1990, 1991, 1992, 1993, 1994, 1995, 1996, 1997

Geo Vehicles:

  • Prizm 1.6L
    • 1993, 1994, 1995, 1996, 1997