TEST 2: Coolant Shooting Out From Open Radiator
If in TEST 1 the oil isn't mixed with coolant, then the next step is to see if the coolant is being shot out of the radiator when the engine is being cranked.
For this test you'll need to open up the radiator and crank the engine. Before you do that, you need to make sure that the engine is completely cold. So is the engine in your 2.5L Dodge Dakota has been running for any amount of time, let it cool down before you do this test.
The normal (and expected) test result is for the coolant to remain undisturbed as the engine is being cranked.
Let's get started.
Remove the radiator's cap. Check to see if there is coolant in the radiator. If the radiator is empty... add some water or coolant to bring it up to the radiator's neck level.
Crank the engine with the help of helper, while you stand at a safe distance from the open radiator.
You'll see one of two results:
1.) The water or coolant inside the radiator will shoot up and out of the now open radiator.
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 radiator.
OK, now that the testing part is done... let's take a look at what your results mean:
CASE 1: The coolant bubbled out or shot out from the radiator: This unfortunate test result tells you, without a shadow of a doubt, that your Dodge Dakota's head gasket is blown.
This test result only happens when the head gasket has blown and/or the cylinder head has warped due to the engine overheating. No further testing is required.
The normal/correct test result is for the coolant to remain undisturbed (inside the radiator) no matter how long you crank the cold engine.
CASE 2: The coolant DID NOT bubble out NOR shoot out from the radiator: If cranking the engine had no visible effect on the level of the coolant in the open radiator... this is normal.
If you were to ask 10 persons, what is the most common symptom of a blown head gasket, 9 out 10 would say, without hesitation, engine oil mixing with coolant and engine compression/ combustion gases shooting out of an open radiator neck... and yes they would be right but not in all of the cases. There are times when this doesn't happen and so the next test will help to further verify this, GO TO: TEST 3: Engine Compression Test.
TEST 3: Engine Compression Test
Every now and then the head gasket will burn between two cylinders. The end result of this type of head gasket failure is that your 2.5L 4 cylinder will 'crank but will not start'.
So, if the engine in your Dodge Dakota starts and runs, skip this test section and go to: TEST 4: Using A Chemical Block Tester (Combustion Leak Tester).
It's been my experience (when I have seen this particular problem occur) that the engine oil won't be mixed with coolant and that the coolant won't be shot out of the radiator (with its cap removed).
To be a bit more specific: The engine won't start because it will have 0 PSI compression on those two side-by-side cylinders (where the head gasket is burned).
Alright, these are the test steps:
Remove all four spark plugs.
Label the spark plug wires so that you won't lose their firing order.
Thread in the compression tester by hand, on the first spark plug hole you're gonna's 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.
Have a helper crank the engine. Your job is to keep your eyeballs on the compression tester. The needle will climb, as the engine cranks, till it reaches the maximum cylinder compression. At the point 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 image in the image viewer to help you identify the cylinder). Repeat the above steps in the remaining 3 cylinders.
Let's take a look at what your test results mean:
CASE 1: All cylinder's had compression. This is the correct and expected test result and confirms that the head gasket is not burned between two adjacent cylinders.
If you'd like to interpret those test results, take a look at this tutorial: How To Test Engine Compression (1993-2002 2.5L Dodge Dakota).
CASE 2: Two side by side cylinders had 0 PSI compression. This test result tells you that the head gasket is burned on your 2.5L Dodge Dakota.