TEST 2: Exhaust Gases Shooting Out Of The Radiator
This next test requires no tools, since all you need to do is remove the radiator cap and then crank the engine to see if coolant is forcefully expelled from the now open radiator.
Cranking the engine, with the radiator open, should have no effect on the coolant inside the radiator.
But if one or both head gaskets are blown, then compression pressures are going to escape into the engine's cooling system and will cause the coolant in the radiator to shoot out as the engine is being cranked.
CAUTION: Be careful! Do not remove the radiator cap with a hot engine! If your min-van's engine has been running for any length of time, let it cool down completely before removing the cap from the radiator.
Let's get started:
- 1
Remove the radiator cap from the radiator.
- 2
Check the coolant level. If the radiator is not full, then top it off with water.
- 3
Have your helper to 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 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 radiator.
Let's examine your test result:
CASE 1: The coolant shot out from the radiator as the engine was cranked. This result confirms that one or both head gaskets are blown on your 3.8L V6 equipped Buick (Oldsmobile, Pontiac) vehicle.
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 or starts but runs with a misfire, go to: TEST 3: Cylinder Compression Test.
If the engine runs but overheats, go to: TEST 4: Using A Chemical Block Tester (Combustion Leak Tester).
TEST 3: Cylinder Compression Test
The compression test will find out if the head gasket is blown at a point between two cylinders.
When this type of head gasket failure occurs, you'll have two 'dead' (misfiring) side-by-side engine cylinders.
The photo at the beginning of this tutorial (page 1 of this tutorial) shows a head gasket that has suffered this type of failure.
OK, these are the test steps:
- 1
Disconnect the ignition coil from its electrical connector. This will disable the ignition system and is an important safety precaution.
- 2
Disconnect the fuel pump relay from its electrical connector.
- 3
Disconnect all spark plug wires (from their spark plugs).
Mark the spark plug wires with the cylinder number they belong to, so you won't lose their firing order. - 4
Remove all of the spark plugs.
- 5
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. - 6
Have a helper crank the engine as you observe the compression tester.
- 7
When the tester's needle stops climbing, have your assistant stop cranking the engine.
- 8
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).
- 9
Remove the compression tester and repeat the above steps in the remaining cylinders.
OK, let's take a look at what your results mean:
CASE 1: All cylinder compression readings where normal. This is the correct test result and it confirms that both head gaskets are OK (not 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 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.
