How To Test For A Blown Head Gasket (1990-2007 3.0L V6 Ford Taurus, Mercury Sable)

If you suspect a blown head gasket on your 3.0L V6 Ford Taurus or Mercury Sable, in this tutorial, I'm going to show you how you can do 4 tests that will help you pinpoint the problem to a blown head gasket.

Now, hopefully you don't have a blown head gasket on your hands, but if you do, two of these tests don't require any tools to get done and can be done under 10 minutes.

The other two do need tools. One of them is an engine compression test, which requires a compression tester, and the other is a block test that requires a block tester, also known as a combustion leak detector.

All of the tests are explained in a step-by-step manner to help you find out quickly if your Taurus or Sable has a blown head gasket or not.

APPLIES TO: This tutorial applies to the following vehicles:

• 3.0L V6 Ford Taurus: 1990, 1991, 1992, 1993, 1994, 1995, 1996, 1997, 1998, 1999, 2000, 2001, 2002, 2003, 2004, 2005, 2006, 2007.
• 3.0L V6 Mercury Sable: 1990, 1991, 1992, 1993, 1994, 1995, 1996, 1997, 1998, 1999, 2000, 2001, 2002, 2003, 2004, 2005.

Symptoms Of A Blown Head Gasket

Most of the time, a blown head gasket happens because the engine got way too hot. And when one or both of the head gaskets fail, you're usually gonna see one or more of these symptoms show up:

• Overheating: The engine runs hot, and you can't find an obvious reason for it.
• Oil and coolant mixing: The oil turns a milky color —looks like coffee with way too much creamer— from coolant leaking into the crankcase.
• White exhaust smoke: Thick, white smoke coming out of the tailpipe from antifreeze burning inside the cylinders.
• No-start condition: The engine will crank, but it just won't fire up.
• Cooling system overpressure: The coolant expansion tank gets overpressurized and starts pushing coolant out whenever the engine idles or after you shut it off.

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

The very first thing a technician will usually do at the shop to check for a blown head gasket is pull out the engine oil dipstick and look at the condition of the oil on it.

Eight times out of ten, when one or both head gaskets have failed, coolant will have entered the crankcase.

This causes the oil to mix with the coolant, turning into something that looks like coffee with way too much creamer.

So for our first test, we'll pull out the dipstick and see what the engine oil looks like.

Let's get going:

1. 1

   Open the hood.

2. 2

   Pull out the engine's oil dipstick.

3. 3

   Check the color of the oil.

4. 4

   You'll see one of two things:
   
   1.) The engine oil will be a creamy tan/off white color and as thick as syrup.
   
   2.) The engine oil will be a normal color and viscosity.

Now, let's find out what each of the two results mean:

CASE 1: The color of the oil is a tan/off white color. This is not good and proves beyond a shadow of a doubt that one or both head gaskets are blown on your 3.0L Ford Taurus or Mercury Sable.

CASE 2: The color of the engine oil is normal. So far so good, but you're not out of the woods yet. You'll need to do the other two tests to further confirm a bad head gasket or exonerate the head gasket. Go to: TEST 2: Exhaust Gases Shooting Out Of The Coolant Expansion Tank.

TEST 2: Exhaust Gases Shooting Out Of The Coolant Expansion Tank

As the engine runs, the combustion cycle creates several pressures (compression, combustion, exhaust, etc.). Under normal conditions, the head gasket seals these pressures inside the cylinders and keeps them out of the cooling system.

If one or both head gaskets fail, that seal is lost. Combustion gases can then escape through the coolant passages in the head and block and enter the cooling system.

If the first test shows the engine oil isn't contaminated with coolant, the next step is to check whether compression and exhaust gases are leaking into the cooling system.

You can do this by removing the cap from the coolant expansion tank and having a helper crank the engine.

• If the coolant is pushed out forcefully from the expansion tank, one or both head gaskets are blown.
• If the coolant stays undisturbed in the tank, the result is normal.

CAUTION: If the engine has been running, allow it to cool down completely before removing the coolant expansion tank cap. Opening it hot can cause serious burns from escaping coolant. To speed up the process of cooling the engine down, place a fan over it.

Here's what to do:

1. 1

   Take off the cap from the coolant expansion tank.
   
   Make sure the tank has enough coolant. If it's low or empty, add water or coolant until it reaches the proper level.

2. 2

   Have your helper crank the engine while you watch the coolant level from a safe distance.

3. 3

   You'll get one of two results:
   
   1.) The coolant inside the expansion tank shoots up or bubbles out.
   
   2.) The coolant level remains undisturbed —cranking the engine has no effect.

Here's how to read the results:

CASE 1: The coolant bubbled up or shot out. This is bad news —it confirms, without a doubt, that one or both head gaskets on your 3.0L V6 Ford Taurus or Mercury Sable have failed.

CASE 2: The coolant did not bubble or shoot out. This is the correct and expected result.

If your Taurus (or Sable) starts and runs but overheats for no clear reason, go to: TEST 4: Using A Chemical Block Tester (Combustion Leak Tester).

If your Taurus (or Sable) starts and runs but has a misfire, go to: TEST 3: Doing A Compression Test.

TEST 3: Doing A Compression Test

It's not uncommon on these V6 engines for a head gasket to fail right between two side-by-side cylinders on the same bank.

When this happens, the engine will still start and run, but those two cylinders lose compression —leaving you with two dead cylinders and a cylinder misfire.

In fact, if you look at the blown head gasket image at the beginning of this tutorial, you'll see it burned through in a spot right between two cylinders.

To pinpoint this type of head gasket failure, a cylinder compression test is needed.

NOTE: You can find a more detailed explanation of the cylinder compression test —along with how to read the results— in this tutorial: How To Do And Interpret An Engine Compression Test (1990-2007 3.0L V6 Ford Taurus, Mercury Sable).

OK, here's what you need to do:

1. 1

   Disable the ignition system.
   
   You can easily accomplish this disconnecting the ignition coil's electrical connector (if your vehicle has a distributor) or the ignition coil pack's electrical connector.

2. 2

   Disable the fuel system. It's important that fuel not be injected into the engine.
   
   You can do this by removing the fuel pump relay or the fuel pump fuse.

3. 3

   Disconnect all spark plug wires (from their spark plugs) and then take out all of the spark plugs.
   
   NOTE: Before you remove the spark plug wires, label them so that you'll be able to easily reconnect them to their proper original locations.

4. 4

   Thread in the compression tester by hand, on the first spark plug hole you're gonna' start with.
   
   Do not use any tools to tighten the compression tester. Hand tightening the compression tester is more than enough to get the proper results.

5. 5

   Have a helper crank the engine while you observe the compression tester.

6. 6

   Once the gauge's needle stops climbing, have your assistant stop cranking the engine.

7. 7

   Write down the reading and what cylinder it belongs to (you can use the image in the image viewer to help you identify the cylinder) on a piece of paper.

8. 8

   Remove the compression tester and repeat the above steps in the remaining cylinders.

OK, let's take a look at what your results mean:

CASE 1: All cylinder compression readings where similar. These compression gauge readings confirm that the head gaskets are OK and not burned at a point between two cylinders.

If you still suspect that you've got a blown head gasket on your hands, especially if the engine overheated recently, your next step is to do a block test with a combustion leak detector. 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 reading confirms that the head gasket is burned thru' at the point between those two cylinders. You'll need to replace both head gaskets.

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

Sometimes a head gasket fails, but the first three tests don't catch it.

In other words, even though one of the gaskets is blown, the coolant isn't mixing with the oil, the radiator isn't pushing coolant out of the tank while cranking the engine, and compression checks out fine —yet the engine still overheats for no clear reason.

When you run into one of these tough cases, the sure way to confirm a blown head gasket is by doing a block test with a combustion leak tester (most commonly called a block tester).

You'll need to buy or borrow the tester, but it's worth it. This tool gives you a solid, accurate answer.

Here's the basic idea of how it works:

• A blue chemical solution is poured into the tester (see photo above).
• The tester is set on the open expansion tank neck. You may have to drain a little coolant to let the tool pull in radiator air.
• Start the engine.
• Squeeze the rubber bulb to draw air through the fluid chambers. The bubbling air reacts with the chemical.
• If the fluid changes from blue to yellow (on gasoline engines), combustion gases are present in the engine's cooling system. That means a blown head gasket, cracked block, or cracked cylinder head.
• If the fluid stays blue, then those issues are not present.

You can get the chemical and block tester at most auto parts stores or here:

Frequently Asked Questions

1.)  Do I need to remove both cylinder head?

Yes, if you have confirmed that the engine has a head gasket failure, you have to remove and check both cylinder heads for cracks and warpage.

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 both cylinder heads! You should never reinstall the cylinder head without first having an automotive machine shop resurface it. Especially if your Ford's engine overheated.

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

More 3.0L V6 Ford Taurus Diagnostic Tutorials

You can find a complete list of 3.0L V6 Ford Taurus and Mercury Sable diagnostic tutorials in this index:

• 3.0L V6 Ford Taurus Index Of Articles.

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

• How To Test The Fuel Injectors (1991-1995 3.0L Ford Taurus).
• How To Test The Alternator (1994-1995 3.0L V6 Ford Taurus).
• How To Test The Fuel Pump (1990-2000 3.0L Ford Taurus).
• Constant Control Relay Module Pinout (1996-1997 3.0L Ford Taurus).