TEST 2: Coolant Shooting Out From Opened Radiator
In this test section, we're going to remove the cap from the pressurized coolant tank (see photo above) and then we're going to crank the engine to see if the engine coolant is going to be shot out of it.
The second most common symptom of a blown head gasket is cylinder compression pressures leaking into the engine cooling system.
We can easily confirm this by simply removing the cap from the pressurized coolant tank and then cranking the engine.
If combustion pressures are leaking into the engine cooling system, then the engine coolant will be shot out the coolant tank as it's being cranked.
If the compression pressures are not leaking into the engine cooling system then you'll notice that the engine coolant will not be disturbed.
NOTE: Your 2.4L equipped GM vehicle does not come equipped with a radiator that has a cap on it. Instead it comes equipped with a pressurized coolant tank that connects to the radiator. It's the cap on this pressurized coolant tank that we'll be removing to perform the test in this section.
IMPORTANT: Never open or remove the cap from the pressurized coolant reservoir 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
Remove the coolant reservoir's cap. Check to see if there is coolant in it and if it's empty, add some water or coolant.
- 2
Crank the engine with the help of helper, while you stand at a safe distance from the open coolant tank.
- 3
You'll see one of two results:
1.) The water or coolant inside the opened coolant reservoir 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.
Let's examine your test results:
CASE 1: Coolant shot out of the opened reservoir tank as you cranked the engine. This test result confirms that the head gasket is blown.
CASE 2: The coolant in the reservoir WAS NOT disturbed as you cranked the engine. This is the correct and expected test result. It confirms that compression pressures are not leaking into your engine cooling system.
If the engine in your vehicle is not starting then your next step is to test engine compression. For this test go to: TEST 3: Engine Compression Test.
If the engine in your vehicle is starting (and is overheating) 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
IMPORTANT: This test only applies if your 2.4L equipped GM vehicle is cranking but not starting.
In this test section, we're going to test the compression of all four cylinders.
The purpose of this test is to see if the head gasket has burned between two cylinders.
If the head gasket has burned between two cylinders then you're going to have 2 side-by-side dead cylinders that will cause the engine to not start.
By dead I mean that the compression value of each cylinder will be 0 PSI because the compression of one cylinder is escaping to the other and vice versa as the engine is being cranked.
These are the test steps:
- 1
Remove all four spark plugs.
- 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
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. - 4
Write down the reading and what cylinder it belongs to (you can use the illustration above to help you identify the cylinder).
- 5
Repeat the above steps in the remaining cylinders.
Let's examine your test results:
CASE 1: The compression values of all cylinders were similar. This is the correct and expected test result and lets you know that he had gasket is not burned between two side-by-side cylinders.
If the engine is cranking but not starting, this test result lets you know that the head gasket is not behind this problem.
CASE 2: Two side-by-side cylinders have 0 PSI compression. This test result confirms that the head gasket is blown since it has burned between two side-by-side cylinders.
