How To Test For A Blown Head Gasket (1994-2005 3.1L V6 Buick Century)

Testing for a blown head gasket on your 3.1L V6 Buick Century isn't difficult. In this tutorial, I'm going to explain the four tests you can perform to find out if the engine has a blown head gasket.

Two of these tests can be done in less than five minutes and don't require any tools whatsoever. The other two are: a compression test using an engine compression tester, and the other is a block test performed with a combustion leak tester.

All of the test steps are explained in a step-by-step manner so that you can easily and quickly find out if you do have a blown head gasket on your 3.1L V6 Buick Century.

APPLIES TO: This tutorial applies to the following vehicles:

• 3.1L V6 Buick Century: 1994, 1995, 1996, 1997, 1998, 1999, 2000, 2001, 2002, 2003, 2004, 2005.

Symptoms Of A Blown Head Gasket

Over the years, I've found that most head gasket failures fall into one of two categories:

1. The head gasket fails and the engine won't start.
2. The engine starts and runs, but it overheats within a few minutes because of the blown head gasket.

If your 3.1L V6 Buick Century has a blown head gasket, you'll usually notice one or more of the following symptoms:

• The engine overheats for no apparent reason, even though the cooling system components (such as the radiator fan, water pump, thermostat, etc.) are working properly.
• Thick white smoke comes out of the tailpipe and has the sweet smell of burning coolant.
• The engine cranks but won't start.
• The engine oil has a milky, light-brown or whitish color because it's mixed with coolant.

TEST 1: Engine Oil The Color Of Coffee With Too Much Creamer

One of the most common signs of a blown head gasket on your 3.1L V6 Buick Century is coolant leaking into the crankcase and mixing with the engine oil.

When coolant and engine oil mix together, the oil takes on a milky, creamy color. I often describe it as looking like coffee with too much creamer.

To get our blown head gasket tests going, our first test is to eyeball the oil on the dipstick. Here's how to interpret what you may find:

• If the oil has a milky, coffee-with-too-much-creamer color, you can conclude that coolant has mixed with the engine oil and that you've got a blown head gasket on your hands.
• If the oil has its normal color and consistency, we won't rule out a blown head gasket just yet. We'll move on to the next test.

Let's get started.

1. 1

   Open the hood.

2. 2

   Pull out the engine oil dipstick.

3. 3

   Check the color of the oil sticking to the engine oil dipstick.

4. 4

   You'll see one of two results:
   
   1.) The engine oil looks like coffee with too much creamer.
   
   2.) The engine oil is its usual normal color.

Alright, let's analyze your test result:

CASE 1: The engine oil has the color of coffee with too much creamer. This test result confirms that the head gasket is blown on your 3.1L V6 Buick Century.

CASE 2: The color of the engine oil is normal. This is the correct and expected test result.

The next test is to see if the engine's compression pressures are escaping into the engine's cooling system (radiator). For this test go to: TEST 2: Coolant Shooting Out From Open Radiator.

TEST 2: Coolant Shooting Out From Open Radiator

Another common way a head gasket fails is by allowing combustion pressure to leak into your engine's cooling system.

You can check for this by removing the radiator cap (only when the engine is completely cold) and then having a helper crank the engine while you watch the coolant inside the radiator.

If the head gasket is blown and combustion gases are entering the cooling system, you'll usually see the coolant being forced up and out of the radiator neck as the engine is cranked.

If the coolant stays calm (undisturbed) and doesn't gush or bubble violently out of the radiator, then this particular test indicates that the head gasket isn't leaking combustion pressure into the cooling system.

IMPORTANT: Never remove the radiator cap if the engine is hot or even warm. Always let the engine cool down completely before removing the cap. Otherwise, hot coolant can spray out under pressure and cause serious burns.

Let's get started:

1. 1

   Remove the radiator cap from the radiator.
   
   Check the coolant level and if necessary add some water or coolant.

2. 2

   Have your helper crank the engine while you stand at a safe distance from the open radiator.

3. 3

   You'll see one of two results:
   
   1.) The water or coolant inside the radiator will shoot out.
   
   2.) The coolant remained undisturbed. In other words, cranking the engine will have no effect on the level of the water or coolant in the radiator.

Let's examine your test result:

CASE 1: The coolant shot out from the open radiator as you cranked the engine. This confirms that you've got a blown head gasket on your 3.1L V6 Buick Century.

CASE 2: The coolant DID NOT shoot out from the open radiator. This is the correct and expected test result.

If your Buick Century starts but runs with a misfire, then next step is to test engine compression. For this test go to: TEST 3: Engine Compression Test.

If the engine starts but overheats almost immediately, then your next step is to do a 'block' test. For this test go to: TEST 4: Using A Chemical Block Tester (Combustion Leak Tester).

TEST 3: Engine Compression Test

In some cases, especially if the engine has severely overheated, one of the two head gaskets will fail between two side-by-side cylinders.

When this happens, both cylinders will have little or no compression because the compression pressure from one cylinder escapes into the other through the damaged section of the head gasket, and vice versa.

On the 3.1L V6 Buick Century, the most common symptom of this type of head gasket failure is an engine that starts and runs, but runs rough (misfires) because those two side-by-side cylinders are misfiring.

The good news is that this type of head gasket failure is easy to identify with a simple engine compression test.

NOTE: You can find the engine compression test explained in more detail and how to interpret its test results in this tutorial: How To Test Engine Compression (1994-2005 3.1L V6 Buick Century).

These are the test steps:

1. 1

   Disable the ignition system by disconnecting the ignition coil pack 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: Every cylinder produced a compression reading above 0 PSI. This is the normal test result and tells you that the head gaskets are not leaking compression between any two neighboring cylinders.

Your next step is to perform a chemical block test with a combustion leak tester. Go to: TEST 4: Using A Chemical Block Tester (Combustion Leak Tester).

CASE 2: Two neighboring cylinders had 0 PSI compression. This confirms that the head gasket has failed between those two cylinders, allowing compression to leak from one cylinder into the other.

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

It's not uncommon for a blown head gasket to be in its early stages of failure. When this happens, it may not cause any of the symptoms that the previous three tests are designed to detect.

In other words, you won't see coolant mixed with the engine oil. You won't see combustion pressure forcing coolant out of the radiator. And all six cylinders will still have good compression.

Yet, as soon as you start the engine, it overheats within a few minutes for no apparent reason.

In these cases, the only way to confirm that the overheating problem is being caused by a blown head gasket is to perform a block test with a combustion leak tester.

This is the very same test an auto repair shop will use to confirm a head gasket failure, and it's something you can easily do yourself.

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:

More 3.1L V6 Buick Century Diagnostic Tutorials

You can find a complete list of diagnostics tutorials for your 3.1L V6 Buick Century in this index:

• 3.1L V6 Buick Century Index of Articles.

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

• How To Test The 24X Crankshaft Position Sensor (1994-2005 3.1L V6 Buick Century)..
• How To Test The TPS With A Multimeter (1997-2005 3.1L V6 Buick Century).
• Common Causes Of Spark Plug Failure (1994-2005 3.1L V6 Buick Century).
• How To Test Engine Compression (1994-2005 3.1L V6 Buick Century).