TEST 2: Coolant Shooting Out Of Radiator

Coolant Shooting Out Of Radiator. Checking To See If The Oil Is Mixed With Coolant (4.2L Ford E150, E250, F150)

Another important job the head gaskets accomplish is to keep the combustion pressures and exhaust gases within the cylinder and from exiting into the coolant and oil passages in the block.

So, when a head gasket gets blown, the second most common end-result is compression/combustion pressures and gases escaping into the block coolant passages and into cooling system (by cooling system I mean the radiator).

This is another very easy test to do and these are the steps:

  1. 1

    Remove the radiator cap from the radiator. The engine should be completely cold before you open the radiator cap. Opening the radiator cap on a hot engine can spray hot coolant all over you and severely burn you.

  2. 2

    If the coolant level is low, top it off before proceeding.

    You don't have to add coolant, just add water.

  3. 3

    Stand at a safe distance from the engine but within view of the radiator.

  4. 4

    When ready, have your helper crank the engine as you observe the radiator's neck.

  5. 5

    You'll see one of two results: The coolant shoots out violently when the engine was cranked or the coolant was not disturbed at all.

Let's take a look at your test results:

CASE 1: The coolant shot out of the radiator. This confirms beyond a shadow of a doubt that you do have a blown head gasket on your hands.

CASE 2: The coolant DID NOT shoot out of the radiator. So far so good. In TEST 1, you confirmed that coolant isn't mixing with the engine oil. In this test, you have confirmed that no exhaust gases are escaping thru' the radiator...

If you still think that you do have a blown head gasket on your 4.2L Ford F150 (4.2L E150 or 4.2L E250), read the next test. Go to:TEST 3: Engine Compression Test.

TEST 3: Engine Compression Test

Engine Compression Test. How To Test For A Blown Head Gasket (4.2L Ford E150, E250, F150)

On some occasions, when the head gaskets gets blown, it burns right between two cylinders. The end result is the compression from one cylinder escaping into the other and vice versa, but coolant doesn't pass into the crankcase nor does the compression escape into the block coolant passages.

To be more specific, when this happens the oil doesn't get mixed with coolant and the compression/exhaust pressures don't get pushed out an open radiator.

To test to see if the head gasket is burned between two side-by-side cylinders (of the same bank), we need to do a compression test.

These are the steps:

  1. 1

    Disable the fuel system and the ignition system.

    You can easily accomplish this disconnecting the ignition coil pack from its electrical connector and removing the fuel pump relay.

  2. 2

    Remove the spark plugs.

    Before you do, label all of the spark plug wires with their cylinder numbers so that you can connect back to the correct spark plug when done.

  3. 3

    Install the compression tester (hand tight only) on the first cylinder you're gonna' test.

  4. 4

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

  5. 5

    Write down the compression readings. You can use the illustration above to record the number of the cylinder.

  6. 6

    Repeat steps 1 through 5 on the next cylinders.

Let's examine your test results:

CASE 1: You got 2 side by side (adjacent) cylinders with 0 PSI. This confirms beyond a shadow of a doubt that you do have a blown head gasket on your hands.

CASE 2: All cylinders had sufficient compression. So far so good. All the tests you've done up until this point tell you that you don't have blown head gasket on your hands.

But, if you still suspect that you have a blown head gasket, I suggest doing a chemical block test as explained in the next test section: TEST 4: Using A Chemical Block Tester (Combustion Leak Tester).

Ford Vehicles:

  • E150 4.2L
    • 1997, 1998, 1999, 2000, 2001, 2002, 2003
  • E250 4.2L
    • 1997, 1999, 2000, 2001, 2002, 2003
  • F150 4.2L
    • 1997, 1998, 1999, 2000, 2001, 2002, 2003, 2004, 2005, 2006