How To Test For A Blown Head Gasket (1991, 1992, 1993, 1994, 1995, 1996, 1997, 1998, 1999, 2000, 2001, 2002, 2003, 2004, 2005, 2006, 2007, 2008, 2009, 2010 4.0L Ford Explorer, Aerostar, And Mercury Mountaineer)

Checking whether your 4.0L Ford Explorer (Aerostar, Mountaineer) has a blown head gasket can be done with one of four different tests and in this article I'll show you how to do them and how to interpret the results you'll obtain from them.

NOTE: You can find the 4.0L Ford Ranger (Mazda B4000) blown head gasket tests here:

APPLIES TO: This tutorial applies to the following vehicles:

  • 4.0L V6 Ford Aerostar: 1991, 1992, 1993, 1994, 1995, 1996, 1997.
  • 4.0L V6 Ford Explorer: 1991, 1992, 1993, 1994, 1995, 1996, 1997, 1998, 1999, 2000, 2001, 2002, 2003, 2004, 2005, 2006, 2007, 2008, 2009, 2010.
  • 4.0L V6 Mercury Mountaineer: 1997, 1998, 1999, 2000, 2001, 2002, 2003, 2004, 2005, 2006, 2007, 2008, 2009, 2010.

En Español You can find this tutorial in Spanish here: Cómo Probar El Empaque De La Cabeza (Ford 4.0L) (at: autotecnico-online.com).

Important Tips

To successfully accomplish the tests in this article, I suggest you follow these tips:

TIP 1: Read the entire article first. The first two tests can be done in under 10 minutes, if you know what you're looking and testing for.

TIP 2: You'll need an engine compression tester for TEST 3.

TIP 3: You'll be working around a cranking engine as you perform TEST 2 and TEST 3, so be careful and take all necessary safety precautions.

Symptoms Of A Blown Head Gasket

A head gasket failure will usually cause one of two issues:

  • An engine no-start problem.
  • The engine starts and runs, but overheats for no apparent reason.

If the engine starts and runs but has suffered a head gasket failure, you'll see one or more of the following symptoms:

  • Your 4.0L Ford Explorer (Aerostar, Mountaineer) is overheating. You know it's not the fan (or fan clutch) or thermostat.
  • White smoke is coming out of the tail-pipe and it smells like anti-freeze being cooked.
  • Your 4.0L Ford Explorer (Aerostar, Mountaineer) won't start.
    • You have already verified it's not an ignition system problem because you have spark coming out at all of the spark plug wires.
    • You know it's not a lack of fuel, because you have verified that the fuel pump is delivering fuel to the fuel injectors.
  • The engine oil is thick and tan to off-white color (mixed with coolant).

In case you're wondering, the most common cause of a blown head gasket is that the engine overheated because:

  1. The fan clutch or fan motor is not working.
  2. All of the coolant leaked out of the engine and you kept driving it this way.
  3. The thermostat went bad and is stuck closed and the coolant could not circulate.

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

Oil The Color Of Coffee With Too Much Cream. How To Test For A Blown Head Gasket (1991, 1992, 1993, 1994, 1995, 1996, 1997, 1998, 1999, 2000, 2001, 2002, 2003, 2004, 2005, 2006, 2007, 2008, 2009, 2010 4.0L Ford Explorer, Aerostar, And Mercury Mountaineer)

One of the tell tale signs of a blown head gasket is coolant mixing with the engine oil. The end result of this failure is engine oil looking like coffee with too much creamer.

Your first test will be to confirm whether this has happened or not by checking the condition of the engine oil sticking to the engine oil dipstick.

This is the test:

  1. 1

    Open the hood.

  2. 2

    Pull out the engine's 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 will be a creamy tan/off white color and as thick as syrup.

    2.) The engine oil is a normal color and viscosity.

This is what the color of the engine oil means:

CASE 1: The color of the oil is a tan/off white color. This is bad news and indicates that your 4.0L Explorer (Aerostar, Mountaineer) overheating to the point the one (or both) of the head gaskets burned.

CASE 2: The color of the engine oil is normal. So far so good, but this result doesn't really confirm that the head gaskets are OK.

The next test is to see if the engine's compression/combustion gases are escaping thru' the radiator. Go to: TEST 2: Combustion Gases Shooting Out Of The Radiator.

Ford Vehicles:

  • Aerostar 4.0L
    • 1991, 1992, 1993, 1994, 1995, 1996, 1997
  • Explorer 4.0L
    • 1991, 1992, 1993, 1994, 1995, 1996, 1997, 1998, 1999, 2000, 2001, 2002, 2003, 2004, 2005, 2006, 2007, 2008, 2009, 2010

Mercury Vehicles:

  • Mountaineer 4.0L
    • 1998, 1999, 2000, 2001, 2002, 2003, 2004, 2005, 2006, 2007, 2008, 2009, 2010