TEST 2: Coolant Shooting Out From Open Radiator
The second most common end result of a blown head gasket is engine compression pressures escaping into the engine cooling system.
This can be checked by simply removing the cap from the radiator and then cranking the engine.
If the coolant is forcefully shot out of the radiator then we can conclude that one or both of the head gaskets are blown on your 3.9L V6 Dodge Dakota.
The normal test result is for the engine coolant to remain undisturbed as the engine is being cranked with the radiator open.
IMPORTANT: Do not remove the radiator cap from the radiator if the engine is hot or has been running for any length of time. If the engine is hot then let it cool down completely before removing the cap from the radiator.
These are the test steps.
- 1
Remove the radiator's cap.
Check the coolant level in the radiator. If the radiator is empty then add some water or coolant. - 2
Have your helper crank the engine while you stand at a safe distance from the open radiator.
- 3
You'll see one of two results:
1.) The water or coolant inside the radiator will shoot out of the open radiator.
2.) The coolant remained undisturbed. In other words, cranking the engine will have no effect on the level of the Water or coolant in the radiator.
Let's examine your test result:
CASE 1: The coolant shot out from the radiator as you cranked the engine. This confirms that one or both of the head gaskets are blown on your 3.9L V6 Dodge Dakota (Durango).
CASE 2: The coolant DID NOT shoot out from the radiator. This is the correct and expected test result.
The next step is to test the engine compression on your 3.9L V6 Dodge Dakota. For this test go to: TEST 3: Engine Compression Test.
TEST 3: Engine Compression Test
In some cases the head gasket gets burned right between two adjacent cylinders (the photo at the beginning of this tutorial shows exactly this type of condition).
When a head gasket gets blown at a point between two cylinders, those two cylinders will misfire.
To check for this condition we're going to test the compression of all 6 cylinders.
If two side-by-side (at adjacent) cylinders have 0 psi compression, then you can conclude that the head gasket has blown between these two cylinders.
These are the test steps:
- 1
Disable the ignition system by disconnecting the ignition coil from its engine wiring harness connector.
- 2
Remove all six spark plugs.
- 3
Install the compression tester by hand in the spark plug hole of cylinder #1.
Do not use any tools to tighten the compression tester. Hand tightening the compression tester is more than enough to get the proper results. - 4
Have your helper crank the engine.
The needle on the tester will climb as the engine cranks. Once the cylinder reaches its maximum compression the needle will stop climbing.
Once it stops climbing have your helper stop cranking the engine. - 5
Write down the reading and what cylinder it belongs to (you can use the illustration above to help you identify the cylinder).
- 6
Repeat steps 2 through 5 in the remaining cylinders.
Let's take a look at what your test results mean:
CASE 1: All cylinder compression readings were above 0 PSI. This is the correct and expected test result.
Your next step is to perform a block test with a block tester. For this test 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 test result confirms that the head gasket (of that bank of cylinders) is burned at the point between those two cylinders. You'll need to replace the head gasket.
