TEST 2: Exhaust Gases Shooting Out Of The Radiator
Another very common head gasket failure is allowing the engine compression/combustion pressures to escape into the cooling system (and into the radiator). We'll check for this in this test section.
You can easily check for this by removing the radiator cap from the radiator and cranking the engine. If the coolant gets shot out forcefully (as you're cranking the engine), the head gasket is blown.
The correct and expected test result is for the coolant to remain undisturbed (in the radiator) as the engine is being cranked.
CAUTION: Do not remove the radiator cap from the radiator if the engine is hot. If the engine has been running for any length of time, then let it cool down completely before removing the radiator cap!
These are the test steps:
Remove the radiator cap from the radiator.
Check the coolant level and add water if necessary.
Have your helper to crank the engine, 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.
Let's examine your test result:
CASE 1: The coolant bubbled out or shot out from the radiator as the engine was cranked. This result confirms that the head gasket is blown.
CASE 2: The coolant DID NOT bubble out NOR shoot out from the radiator as the engine was cranked. This is the correct test result.
If the engine doesn't start, your next step is: TEST 3: Engine Compression Test.
If the engine starts and runs but overheats, your next test is: TEST 4: Using A Chemical Block Tester (Combustion Leak Tester).
TEST 3: Engine Compression Test
The head gasket in the photo at the start of this tutorial failed between two side by side cylinders. The end result of this type of head gasket failure is that both those cylinders will have zero compression.
While this type of head gasket failure doesn't happen every day, it's common enough that we need to check for it. You can easily do this by doing an engine compression test and in this section, I'll walk you through the compression test.
NOTE: You can find the engine compression test and how to interpret its results explained in more detail here: Testing Engine Compression (1996-2007 2.4L Chrysler, Dodge, Plymouth Mini-Van).
OK, these are the test steps:
Disconnect the ignition coil from its electrical connectors. This is will disable the ignition system and is an important safety precaution.
Disconnect all spark plug wires (from their spark plugs).
Remove all of the spark plugs.
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.
Have a helper crank the engine as you observe the compression tester.
When the gauge's needle stops climbing, have your assistant stop cranking the engine.
Write down the reading and what cylinder it belongs to on a piece of paper (you can use the illustration above to help you identify the cylinder).
Remove the compression tester and repeat the above steps in the remaining cylinders.
Let's examine what your results mean:
CASE 1: All cylinder compression readings where normal. This is the correct test result and it confirms that the head gasket isn't burned at a spot between two side-by-side cylinders.
If you still suspect a blown head gasket, go to: TEST 4: Using A Chemical Block Tester (Combustion Leak Tester).
CASE 2: Two side by side cylinders had 0 PSI compression. This test result confirms that the head gasket is burned at the point between those two cylinders. Replace the head gasket.