How To Test for a Blown Head Gasket (GM 4.8L, 5.3L, 6.0L)

The end result of severe over-heating is usually a blown head gasket, but not always.

If and/when a head gasket burns or the cylinder head warps, you're gonna' need to check/test for 3 specific things and they are:

  1. Engine oil mixed with coolant.
  2. Exhaust/compression gases and pressures escaping thru' the cooling system.
  3. Cylinder compression escaping from one cylinder into the adjacent one and vice-versa.

In this article, I'll show you what to look for and what to test so that you can confirm that you do indeed have a blown head gasket issue or not.

Here are the main points of this article:

  1. Symptoms of BAD Engine Compression.
  2. TEST 1: Engine Oil Mixed With Coolant.
  3. TEST 2: Coolant Shooting Out Expansion Tank.
  4. TEST 3: Checking Engine Compression.
  5. TEST 4: Using A Chemical Block Tester (Combustion Leak Tester).
  6. Frequently Asked Questions.
  7. More GM 4.8L, 5.3L, 6.0L Tutorials.

En Español Puedes encontrar este tutorial en Español aquí: Cómo Probar Los Empaques de Cabezas (GM 4.8L, 5.3L, 6.0L) (en: autotecnico-online.com).

Symptoms Of A Blown Head Gasket

There are several symptoms of a blown head gasket on your GM pickup, van, or SUV and the one thing they all have in common is that you vehicle over-heated.

At the beginning of the article, I touched on three specific symptoms, here are a couple more:

  1. Overheating.
    1. You may have already checked and/or replaced:
      1. Thermostat.
      2. Water pump.
      3. Radiator.
      4. Repaired any coolant leaks.
      5. Fan Clutch.
  2. Oil mixed with coolant.
    1. This will turn the color of the oil a creamy white color.
    2. No matter how many times the oil gets changed, it immediately turns into this creamy white color.
  3. White smoke coming out of the tail-pipe.
    1. If you're using anti-freeze, you'll smell its sweet smell in the smoke.
  4. Engine cranks, but does not start.
    1. When this happens, you'll notice that everything works, for example:
      1. Fuel pump.
      2. COP ignition coils.
      3. Fuel injectors.
  5. No compression on two side by side cylinders.

TEST 1: Engine Oil Mixed With Coolant

Checking to See if the Oil is Mixed with Coolant (GM 4.8L, 5.3L, 6.0L)

The cylinder head gaskets on your GM pickup, van or SUV are tasked with keeping three very specific components of the engine separate from one another (among several things) and these three are:

  1. Coolant.
  2. Engine oil.
  3. Compression/combustion pressures and gases.

When your vehicle overheats to the point that the aluminum cylinder head warps and/or the head gasket burns... these components will mix.

The most common end result of a blown head gasket is coolant mixing with the engine oil. To check for this, all you have to do is:

  1. Open the hood of the car.
  2. Pull out the engine oil dipstick.
  3. Check the color of the oil sticking to the dipstick.
  4. You'll see one of two things:
    1. The color of the Oil will be a milky white color (like coffee with too much cream).
    2. Or the color of the oil will be its normal color.

Let's take a look at your test results:


CASE 1: The engine oil was a milky white color (like coffee with too much cream). This tells you that the Coolant is mixing with the Oil and that you do have a blown head gasket on your hands.

CASE 2: The engine oil was its normal color. This doesn't confirm anything just yet. You'll need to go to the next test to make sure. Go to TEST 2.