How To Test for a Blown Head Gasket
(Ford 4.0L)

How To Test for a  Blown Head Gasket (Ford 4.0L)

Checking whether your 4.0L Ford Explorer (4.0L Ranger, 4.0L Aerostar, or 4.0L 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.

To get you where you need to be, in this article, here are its contents at a quick glance:

  1. Important Tips.
  2. Symptoms of a Blown Head Gasket.
  3. TEST 1: Oil the Color of Coffee With Too Much Cream.
  4. TEST 2: Combustion Gases Shooting Out of the Radiator.
  5. TEST 3: Cylinder Compression Test.
  6. TEST 4: Using a Chemical Block Tester (Combustion Leak Tester)
  7. More 4.0L Ford Diagnostic Tutorials

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 HEAD GASKET TEST 3.

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

Symptoms of a Blown Head Gasket

The most common cause of a blown head gasket is that the engine overheated because: 1) 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) Thermostat went BAD and is stuck closed and the coolant could not circulate. The most common symptoms a blown head gasket are:

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

TEST 1: Oil the Color
of Coffee With Too Much Cream

Oil the Color of Coffee With Too Much Cream. How To Test for a  Blown Head Gasket (Ford 4.0L)

A blown head gasket is the result of the engine overheating and usually, one of the tell tale signs is coolant mixing with the engine oil. This first test will confirm whether this has happened or not. This is the test:

  1. 1

    Open the hood and pull out the engine's oil dipstick.

  2. 2

    Now, look at the engine oil that's sticking to the dipstick. It will be one of two colors:

    1.) Either the engine oil will be a creamy tan/off white color and as thick as syrup Or...

    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 (or Ranger, 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. 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: Combustion Gases Shooting Out of the Radiator.

Here's why: Most of the time when the vehicle overheats and one of the head gaskets burns... it will let coolant into the crankcase... but not always. Thankfully, there are several more tests that can be done to confirm that the head gasket is blown or exonerate it as the cause of the issue. If in your case this test was inconclusive, the next test is to see if the engine's compression/ combustion gases are escaping thru' the radiator.

Ford Vehicles:

  • Aerostar 4.0L
    • 1993, 1994, 1995, 1996, 1997
  • Explorer 4.0L
    • 1995, 1996, 1997, 1998, 1999, 2000, 2001, 2002, 2003
  • Ranger 4.0L
    • 1993, 1994, 1995, 1996, 1997, 1998, 1999, 2000, 2001, 2002, 2003

Mercury Vehicles:

  • Mountaineer 4.0L
    • 1997, 1998, 1999, 2000, 2001, 2002, 2003

“I bought a perfect second car... a tow truck.”
Rodney Dangerfield

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