How To Test For A Blown Head Gasket (2011-2019 1.6L Ford Fiesta)

TEST 3: Engine Compression Test

In a few cases, the head gasket will suffer some sort of failure but it won't produce any of the issues that the previous three tests are designed to confirm.

In these cases, the engine starts and runs but it overheats within minutes. This can be quite the head-scratcher because the engine seems to overheat for no apparent reason.

If you're facing this particular issue, you're going to need to perform a block test with a combustion leak detector tool (to confirm that it's due to a blown head gasket).

This is the exact same test that the technician at the auto repair shop is going to perform to confirm that the issue is due to a blown head gasket.

These are the test steps:

1. 1

   Disable the ignition system by disconnecting the ignition coil from its engine wiring harness connector.

2. 2

   Remove all of the spark plugs.

3. 3

   Install the compression tester by hand in the spark plug hole of cylinder #1.
   
   Do not use any tools to tighten the compression tester. Hand tightening the compression tester is more than enough to get the proper results.

4. 4

   Have your helper crank the engine.
   
   The needle on the tester will climb as the engine cranks. Once the cylinder reaches its maximum compression the needle will stop climbing.
   
   Once it stops climbing have your helper stop cranking the engine.

5. 5

   Write down the reading and what cylinder it belongs to (you can use the illustration above to help you identify the cylinder).

6. 6

   Repeat steps 3 through 5 in the remaining cylinders.

Let's take a look at what your test results mean:

CASE 1: All cylinder compression readings were above 0 PSI. This is the correct and expected test result.

Your next step is to perform a block test with a block tester. For this test go to: TEST 4: Using A Chemical Block Tester (Combustion Leak Tester).

CASE 2: Two side by side cylinders had 0 PSI compression. This engine compression test result confirms that the head gasket is burned at the point between those two cylinders.

You'll need to replace the head gasket.

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

Some head gasket failures do not produce any of the symptoms that the previous three tests are designed to look for. Typically, the head gasket failure only causes the engine to overheat within minutes of starting it and no other symptoms.

In these cases the only way to confirm that the problem is due to a head gasket failure is to perform a block test with a combustion leak detector tool.

This is the exact same test that the technician at the auto repair shop is going to perform to diagnose the issue and it's a test you can do yourself too.

A block test simply involves using a chemical combustion leak detector tool that checks to see if combustion gases are leaking into the engine cooling system.

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 engine is started.
• 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), then combustion gases are entering the radiator. This 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 a blown head gasket, 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: