TEST 2: Coolant Shooting Out Of Radiator
After quickly checking the color of the oil, the next test was to see if coolant would shoot out of the radiator (with the cap removed) when cranking the engine.
The idea behind this test was to see if the head gasket was blown and letting compression pressures escape thru' the cooling system (which the radiator is a major component of).
This test checks for the second most common end-result of a blown head gasket and it's the next one I'm gonna' suggest to you.
OK, these are the test steps:
- 1
Remove the radiator cap from the radiator.
If the coolant level is low, top it off before proceeding.
IMPORTANT: The engine should be completely cold before you open the radiator cap. Opening the radiator cap on a hot engine can spray hot coolant all over you and severely burn you. - 2
Stand at a safe distance from the engine but within view of the radiator.
- 3
When ready, have your helper crank the engine.
- 4
You'll see one of two results:
1.) The coolant shoots out violently when the engine is cranked.
2.) The coolant is not disturbed at all.
Let's take a look at what your test results mean:
CASE 1: The coolant shot out of the radiator. This confirms beyond a shadow of a doubt that you do have a blown head gasket on your hands.
CASE 2: The coolant DID NOT shoot out of the radiator. So far so good. In TEST 1, you confirmed that coolant isn't mixing with the engine oil. In this test you have confirmed that no exhaust gases are escaping thru' the radiator...
If you still think that you do have a blown head gasket, read the next test. Go to TEST 3
TEST 3: Engine Compression Test
It doesn't happen very often, but every now and then a head gasket gets burned in the spot right between two adjacent cylinders. This results in the compression of one cylinder to escape into the other and vice-versa.
The end result of this condition was an engine that cranks but doesn't start. The way to check this by doing a compression test and it's the 3rd test I'm gonna' recommend you do:
- 1
Disable the fuel system and the ignition system.
- 2
Disconnect the spark plugs wires from the spark plugs.
- 3
Remove the spark plugs.
- 4
Install the compression tester (hand tight only) on the first cylinder you're gonna' test.
- 5
Have a helper crank the engine while you observe the compression tester.
- 6
When the needle stops moving, have your helper stop cranking the engine.
- 7
Write down the compression readings.
- 8
Repeat on the next 3 cylinders.
Let's take a look at what your test results mean:
CASE 1: You got 2 side by side (adjacent) cylinders with 0 PSI. This confirms beyond a shadow of a doubt that you do have a blown head gasket on your hands.
CASE 2: All cylinders had sufficient compression. This is the correct and expected test result.
If you still suspect that your vehicle has a blown head gasket, go to: TEST 4: Using A Chemical Block Tester (Combustion Leak Tester).
