TEST 2: Coolant Shooting Out From Opened Radiator

In this section we're going remove the radiator cap and crank the engine.

What we're looking for is to see if engine coolant is forcefully shot out of the radiator neck while the engine is being cranked.

Now as you're probably already aware, the radiator on your 3.9L V6 equipped GM vehicle does not have an actual radiator neck with a cap on it.

Your particular 3.9L V6 equipped vehicle will either come equipped with a coolant filler neck on the engine itself (see photo 1 of 2).

Or it has no coolant filler neck at all and comes equipped with a pressurized coolant reservoir (see photo 2 of 2 above).

Whether your vehicle comes equipped with a coolant filler neck or the pressurized coolant tank, this test is a piece of cake.

IMPORTANT: Never open or remove the cap from the pressurized coolant reservoir or from the coolant filler neck if the engine is hot. If the engine has been running for any length of time, let it cool down completely. You can also cool down the engine in a matter of 15-20 minutes by placing a running box fan on top of it.

Let's get started:

  1. 1

    Remove the cap from the coolant filler neck or the pressurized coolant tank.

    Check to see if there is coolant in the coolant filler neck or coolant tank. If it's empty, add some water or coolant.

  2. 2

    Crank the engine with the help of helper, while you stand at a safe distance from the open coolant tank or coolant filler neck.

  3. 3

    You'll see one of two results:

    1.) The water or coolant inside the opened coolant reservoir or coolant filler neck will shoot out.

    2.) The coolant will not be disturbed. In other words, cranking the engine will have no effect on the level of the water or coolant in the resevoir or coolant filler neck.

Let's examine your test results:

CASE 1: Coolant shot out of the opened reservoir tank or coolant filler neck as you cranked the engine. This test result confirms that you have a blown head gasket on your 3.9L V6 Chevy Malibu engine.

The normal test result is for the coolant to not be disturbed as you crank the engine.

CASE 2: The coolant in the reservoir or coolant filler neck WAS NOT disturbed as you cranked the engine. This is the correct and expected test result.

If the engine does not start, then your next step is: TEST 3: Engine Compression Test.

If the engine starts and runs but overheats 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

Engine Compression Test. Testing For A Blown Head Gasket (2006, 2007, 2008, 2009, 2010 3.9L Impala, Malibu, Uplander, G6, Montana)

NOTE: If the engine starts and runs but overheats, then you can skip this test and go to TEST 4. This test step only applies if the engine is not starting.

In this section we're going to see if one of the head gaskets is causing the engine to not start.

If one of the head gaskets is causing the engine to not start, it's usually because you have got at least 3 dead cylinders.

These are the test steps:

  1. 1

    Remove all six spark plugs.

    Disable the ignition system by disconnecting the ignition coil pack from its engine wiring harness connector.

  2. 2

    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.

  3. 3

    Have a helper crank the engine. The needle on the tester will climb, as the engine cranks, till the cylinder reaches its maximum compression. Once it stops climbing, have your helper stop cranking the engine.

    On a piece of paper, write down the reading and what cylinder it belongs to (you can use the illustration above to help you identify the cylinder). Repeat the above steps in the remaining cylinders.

Let's examine your test results:

CASE 1: Your compression test results indicate that two or three cylinders have close to or 0 PSI compression. This test result confirms that the head gasket or head gaskets are blown only if the 'engine no start' problem was preceded by a severe overheating problem.

If you want to find out more about how to interpret the engine compression test results you just obtained, check out this tutorial: How To Test The Engine Compression (2006-2010 3.9L V6 Engine).

CASE 2: The compression values of all 6 cylinders were similar. This is the correct and expected test result.

Your vehicle's 3.9L V6 engine ‘no start’ problem is not being caused by blown head gaskets.

Chevrolet Vehicles:

  • Impala 3.9L
    • 2006, 2007, 2008, 2009, 2010
  • Malibu 3.9L
    • 2006, 2007
  • Uplander 3.9L
    • 2006, 2007, 2008

Pontiac Vehicles:

  • G6 3.5L
    • 2006, 2007, 2008, 2009
  • Montana 3.9L
    • 2006, 2007, 2008, 2009