How To Test A GM 4.3L, 5.0L, 5.7L Blown Head Gasket

There are so many ways to test for a blown head gasket on your 4.3L, 5.0L, 5.7L GM van (or mini-van, pick up, SUV) that it can get confusing. Well, I'm going to show you three different ways to test for a blown head gasket. These are step-by-step tests that will help you to get to the bottom of the problem.

These are very easy tests to do, as a matter of fact, two of them are done with absolutely no tools at all. The third test is done using a engine compression tester. The fourth is the chemical block test. And as mentioned at the beginning, they are all explained in detail with their test result interpretations included.

En Español You can find this tutorial in Spanish here: Cómo Probar los Empaques de las Cabezas (GM 4.3L, 5.0L, 5.7L) (at:

Symptoms Of A Blown Head Gasket

The most common cause of a blown head gasket is that the engine overheated because: 1) Fan clutch is not working, 2) All of the coolant leaked out of the engine and you kept driving it this way. 3) Thermostat went BAD and is stuck closed and the coolant could not circulate. The most common symptoms a blown head gasket are:

  1. Your 4.3L, 5.0L, 5.7L GM van (or mini-van, pick up, SUV) is overheating. You know it's not the fan (or fan clutch) or thermostat.
  2. White smoke is coming out of the tail-pipe and it smells like anti-freeze being cooked.
  3. Your 4.3L, 5.0L, 5.7L GM van (or mini-van, pick up, SUV) won't start.
    1. You have already verified it's not an ignition system problem because you have spark coming out at all of the spark plug wires.
    2. You know it's not a lack of fuel, because you have verified that the fuel pump is delivering fuel to the fuel injectors.
  4. The engine oil is thick and tan to off-white color (mixed with coolant).

TEST 1: Is The Engine Oil The Color Of ‘Coffee With Too Much Cream’?

Checking to See if the Oil is Mixed with Coolant (GM 4.3L, 5.0L, 5.7L Blown Head Gasket Test)

Before you start, I suggest you take a quick glance at all three tests. The first two can be done under 5 minutes and in the majority of the cases, you probably won't have to do all three tests. If, for example, the first test, proves to you that the head gasket in blown... there's no need to proceed to the 2nd or 3rd test (unless for the sake of knowledge itself).

OK, I'll stop talking and we'll get this show on the road, this is what you need to do:

  1. 1

    Pop the hood on your 4.3L, 5.0L, 5.7L GM van (or mini-van, pick up, SUV) and once open, pull out the engine's oil dipstick.

  2. 2

    Now, check what the color of the oil is and how thick it is. What you're doing is confirming one of two things:

    1.) Either the oil, sticking to the dipstick, is a creamy tan color and is thick as syrup Or...

    2.) The oil is its normal color and viscosity.

Now, let's find out what each of the two results mean:

CASE 1: The color of the oil is a light tan, like coffee with too much cream, this is not good news and positively confirms that the head gasket on your 4.3L, 5.0L, 5.7L GM van (or mini-van, pick up, SUV) is blown. The solution to this problem is replacing both head gaskets.

Why does the oil look like this? Mainly because your 4.3L, 5.0L, 5.7L GM van (or mini-van, pick up, SUV) over-heated and :

1.) The cylinder head (or heads) warped. This warpage causes the head gasket (or gaskets) to burn.

2.) A blown head gasket loses its sealing power/ability and if it's not sealing the oil and coolant ports in both the engine block and the cylinder head this will lead to...

3.) ...this will lead to the coolant entering the engine oil pan.. As both oil and coolant mix... the resulting combination gets thick and becomes an off-white color.

CASE 2: The color of the engine oil is normal, Although this is a good result, you're not out of the woods yet. I suggest doing the two other tests I'm presenting in this article. Go to TEST 2: Are Engine Compression -Exhaust Gases Coming Out Of The Radiator?.

Here's why: Normally (about 90% of the time) when a head gasket gets blown on a 4.3L, 5.0L, 5.7L GM van (or mini-van, pick up, SUV)... coolant will enter into the crankcase and mix with the engine oil. This is not an absolute truth. Thankfully, there are several more tests that you can do to make sure that the head gasket is really blown or not. The next test is to see if the engine's compression/ combustion gases are escaping thru' the radiator.