HEAD GASKET TEST 2: Coolant Shooting Out From Open Radiator
Another of the most common symptoms of a blown head gasket is the engine's compression or combustion gases entering the cooling system. This can easily be tested and in this test step I'll show you how.
A word of caution: If your Honda Civic has been running for an extended amount of time, let the engine cool down for at least an hour, since this test step will ask you to remove the radiator cap. Be careful and remember that a radiator cap should never be removed from a hot radiator.
There's a good chance that your Honda Civic is not starting, in this case you don't have to worry about a hot engine.
- 1
Remove the radiator's cap.
- 2
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. - 3
Now, have a helper crank the engine while you stand at a safe distance from the open radiator.
- 4
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 is a clear indication that the 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.
CASE 2: The coolant DID NOT bubble out NOR shoot out from the radiator. This is the correct and expected test result.
If your Honda Civic cranks but does not start, your next step is to go to: HEAD GASKET TEST 4: Using A Chemical Block Tester (Combustion Leak Tester).
If your Honda Civic starts and runs, but overheats for no apparent reason, go to: HEAD GASKET TEST 3: Engine Compression Test.
HEAD GASKET TEST 3: Engine Compression Test
What leads a lot of folks to misdiagnose a blown head gasket is that, in their particular case, they checked the engine oil and it was not mixed with coolant. They also did the radiator with the cap off test and the engine's compression or combustion gases were not escaping from there.
They never realized that a head gasket can get blown without causing the coolant to mix with the engine oil and without causing combustion gases from entering the cooling system. I have seen this enough to know that one more test has to be done.
How is this possible? Well, this happens because the head gasket has burned at a point between two cylinders (the image at the beginning of this tutorial shows this type of failure), the resulting gap in the head gasket will let only the compression/combustion of one cylinder to leak into the other and vice-versa, but nothing else (like coolant). If this happens, in a Honda Civic, this will cause a no-start condition.
This condition can be very easily verified by doing a compression test. In this test step I'll show you how and more importantly, how to interpret the compression test results to see if the head gasket is burned or not.
These are the test steps:
- 1
Disable the ignition system. This will prevent spark from being created and delivered to the spark plug wires.
You can do this by disconnecting the ignition coil's connector, if the ignition coil is located outside of the distributor on your Honda.
If your Honda Civic has the ignition coil inside the distributor, disconnect the distributor's connectors, and this will disable the ignition coil. - 2
Disconnect all four spark plug wires from their spark plugs.
- 3
Remove all of the spark plugs.
- 4
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. - 5
Have a helper crank the engine while you keep your eyes on the compression tester.
The needle will climb, as the engine cranks, till it reaches the maximum cylinder compression. - 6
At the point the gauge's needle stops climbing, have your helper stop cranking the engine.
- 7
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.
- 8
Repeat the above steps in the remaining 3 cylinders.
If your Honda Civic's head gasket is burned at a location between 2 cylinders, your compression test readings will give you 2 good compression readings and 2 compression readings that will be 0 PSI. Let me give you a more specific example:
Let's say that I tested my Honda Civic and I got the following cylinder compression readings:
- Cylinder #1 = 175 PSI
- Cylinder #2 = 165 PSI
- Cylinder #3 = 0 PSI
- Cylinder #4 = 0 PSI
As you can see from the above compression readings, cylinders #3 and #4 have 0 PSI readings. And this is a clear indication that the head gasket has burned at the point between them both. Now, in your specific case, you may not see those exact same cylinders with 0 PSI readings. It may be #1 and #2 or it may be #2 and #3, the main idea is that whatever cylinders are affected, they will always be side by side.
CASE 1: All cylinder compression readings where normal. These compression gauge readings confirm that the head gasket is OK and not burned at a point between two cylinders.
OK, 3 out of 3 tests have confirmed that the head gasket on your Honda Civic is not blown.
CASE 2: Two side by side cylinders had 0 PSI compression. This engine compression reading confirms that the head gasket is burned thru' at the point between those two cylinders. You will need to replace the head gasket.
