TEST 2: Coolant Shooting Out From Open Radiator
This second test is also a doozy to perform and it doesn't require any tools whatsoever.
What we'll do, is to remove the cap from the radiator and then crank the engine.
The purpose of the test is to see if the coolant will be shot out of the open radiator. If it does get shot out, then you can conclude that you've got a blown head gasket problem on your hands.
The normal and expected test result is for the coolant to remain undisturbed in the radiator as you crank the engine.
IMPORTANT: Do not remove the radiator cap from the radiator if the engine is hot or has been running for any length of time. Let the engine cool down completely before removing the cap from the radiator.
Let's get started:
- 1
Remove the radiator's cap.
Check the coolant level in the radiator. If the radiator is empty then add some water or coolant. - 2
Have your helper crank the engine while you stand at a safe distance from the open radiator.
- 3
You'll see one of two results:
1.) The water or coolant inside the radiator will shoot out of the open radiator.
2.) The coolant remained undisturbed. 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 shot out from the radiator as you cranked the engine. This confirms that one or both head gaskets are blown on your 3.1L Chevrolet (Pontiac).
CASE 2: The coolant DID NOT shoot out from the radiator. This is the correct and expected test result.
If the engine, in your 3.1L V6 Chevrolet (Pontiac), starts but runs with a misfire or doesn't start at all, then next step is to test engine compression. For this test go to: TEST 3: Engine Compression Test.
If the engine starts but overheats almost immediately, 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
Certain head gasket failures cause the gasket itself to burn in a spot right between two adjacent cylinders. The photo at the beginning of this tutorial shows this exact type of failure.
When the head gasket burns between two side-by-side cylinders, those two cylinders will produce 0 compression.
The end result is that your 3.1L V6 engine will only run on 4 cylinders.
The way to test this type of head gasket failure is by doing an engine compression test
NOTE: You can find the compression test explained in more detail here: How To Test The Engine Compression (3.1L V6 Chevrolet, Pontiac).
These are the test steps:
- 1
Disable the ignition system by disconnecting the ignition coil from its engine wiring harness connectors.
- 2
Remove all of the spark plugs.
Before you remove them, label all of the spark plug wires with the cylinder they belong to. - 3
Install the compression tester by hand in the spark plug hole of cylinder #1.
Do not use any tools to tighten the compression tester. Hand tightening the compression tester is more than enough to get the proper results. - 4
Have your helper crank the engine.
The needle on the tester will climb as the engine cranks. Once the cylinder reaches its maximum compression the needle will stop climbing.
Once it stops climbing have your helper stop cranking the engine. - 5
Write down the reading and what cylinder it belongs to (you can use the illustration above to help you identify the cylinder).
- 6
Repeat steps 3 through 5 in the remaining cylinders.
Let's take a look at what your test results mean:
CASE 1: All cylinder compression readings were above 0 PSI. This is the correct and expected test result.
Your next step is to perform a block test with a block tester. For this test go to: TEST 4: Using A Chemical Block Tester (Combustion Leak Tester).
CASE 2: Two side by side cylinders had 0 PSI compression. This engine compression test result confirms that the head gasket (of that bank of cylinders) is burned at the point between those two cylinders.
You'll need to replace both head gaskets.
