How To Test For A Blown Head Gasket (1.5L Toyota Tercel)

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

Using a chemical block tester is the one test that is done when the previous 3 tests have not confirmed a blown head gasket, but the engine overheats for no apparent reason.

You do have to buy (or borrow) the block tester, but this tool is worth every penny since it's a test that gives you a very accurate test result.

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) combustion gases are entering the radiator. This result confirms a head gasket failure, a cracked block, or a cracked cylinder head issue.
• If the blue chemical doesn't change color, you can conclude that you don't have a head gasket failure, 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:

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 your 1.5L Toyota Tercel's cylinder head without first having an automotive machine shop resurface it. Especially if your Tercel's engine overheated.

Now, of course, if you (or the machine shop) have checked it with a straight-edge and it isn't warped then, and only then is the cylinder head not resurfaced.

More 1.5L Toyota Tutorials

There are several more ‘how to’ tutorials that I've written that are 1.5L Toyota Tercel specific that may be of further help. You can find them in this index:

• Toyota 1.5L Index Of Articles.

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

• How To Test The Ignitor -Step By Step (1995-1996 1.5L Toyota Tercel).
• How To Test Engine Compression (1.5L Toyota Tercel).
• How To Test The Fuel Injectors (1995-1996 1.5L Toyota Tercel).