Testing for a blown head gasket on your Chevy Express or GMC Savana van isn't difficult. In this tutorial, I'll walk you thru the 4 tests you can perform to find out.
With the results of your tests, you'll know if your van's V8 engine has a blown head gasket causing it to either overheat or not-start.
By the way, two of those four tests do not require any tools whatsoever.
Contents of this tutorial:
You can find this tutorial in Spanish here: Cómo Probar Los Empaques De Cabeza (2003-2013 V8 Chevrolet Express, GMC Savana (at: autotecnico-online.com).
APPLIES TO: This tutorial applies to the gasoline powered 4.8L, 5.3L, and 6.0L V8 engines only:
- Chevrolet Express 1500, 2500, 3500: 2003, 2004, 2005, 2006, 2007, 2008, 2009, 2010, 2011, 2012, 2013.
- GMC Savana 1500, 2500, 3500: 2003, 2004, 2005, 2006, 2007, 2008, 2009, 2010, 2011, 2012, 2013.
Symptoms Of A Blown Head Gasket
With the head gasket fails, you'll usually have one of two headaches:
- The engine cranks but doesn't start.
- The engine starts but then overheats in no time for no good reason.
If the engine in your van starts and runs and one or both head gaskets are blown, you'll see one or more of the following symptoms:
- Overheating: One of the most noticeable symptoms is engine overheating. A blown head gasket can allow coolant to leak into the combustion chambers or oil passages, leading to inadequate cooling of the engine.
- White Smoke from the Exhaust: If coolant leaks into the combustion chambers, it can be burned along with the fuel, producing white smoke from the exhaust. This is often accompanied by a sweet smell.
- Milky Oil: Coolant mixing with engine oil can result in a milky or frothy appearance on the oil dipstick or under the oil filler cap. This indicates contamination and a potential head gasket leak.
- Loss of Coolant: If there's a head gasket leak, you may notice a gradual decrease in coolant levels without any apparent external leaks. Keep an eye on the coolant reservoir and radiator.
- Poor Engine Performance: A blown head gasket can cause the engine to run poorly, with symptoms such as rough idling, hesitation, or a noticeable decrease in power and acceleration.
- External Coolant Leaks: In some cases, coolant may leak externally from the engine, typically near the head gasket area. Look for signs of coolant puddles or stains under the vehicle.
- Bubbles in the Radiator or Overflow Tank: When the engine is running, air bubbles may be visible in the radiator or overflow tank if there's combustion gas leaking into the cooling system through a blown head gasket.
- Excessive Pressure in Cooling System: A blown head gasket can cause an increase in pressure within the cooling system, leading to bulging hoses, coolant overflow, or even radiator or hose ruptures.
- Compression Loss: A compression test can reveal low compression in one or more cylinders, indicating a potential head gasket failure.
- Check Engine Light: Depending on the severity of the issue, the engine's computer may detect abnormalities related to engine performance or emissions, triggering the check engine light.
TEST 1: Oil The Color Of Coffee With Too Much Creamer
When coolant mixes with engine oil due to a blown head gasket, it can create a mixture that looks similar to coffee with too much creamer. The coolant and oil combine to form a milky or frothy substance, which is easily visible on the oil dipstick or under the oil filler cap.
To start your blown head gasket diagnostic, we'll check the color of the engine oil sticking to the engine oil dipstick.
If it turns out that the engine oil has a milky white color, like coffee with too much creamer, you've got a blown head gasket on your hands.
If the color of the oil is normal (as in not milky white), then you can move on to TEST 2.
Let's get started:
- 1
Open the hood.
- 2
Pull out the engine's oil dipstick.
- 3
Check the color of the oil and how thick it is.
- 4
You'll see one of two things:
1.) The oil on the dipstick is a creamy, off-white color and is thick as syrup.
2.) The oil is its normal color and viscosity.
Let's see what your test result means:
CASE 1: The engine oil looks like 'coffee with too much creamer'. This confirms that one or more of the engine's head gaskets are blown.
CASE 2: The color of the engine oil is normal. This is the correct and expected test result.
The next step is to check to see if compression/exhaust gases are leaking into the cooling system. Go to: TEST 2: Exhaust Gases Shooting Out Of The Radiator.
TEST 2: Exhaust Gases Shooting Out Of The Radiator
A failed head gasket can allow combustion gases or compression pressures to escape into the cooling system of the engine. This can lead to increased pressure within the cooling system, causing symptoms like coolant overflow, bulging hoses, or even radiator or hose ruptures.
One common test to check for this specific issue is to remove the radiator cap and then crank the engine. If one or both head gaskets have failed and are allowing compression pressures into the cooling system, you'll see coolant being forcefully expelled from the radiator.
The correct and expected test result is for the coolant to remain undisturbed (in the radiator) as the engine is being cranked.
CAUTION: Do not remove the radiator cap from the radiator if the engine is hot. If the engine has been running for any length of time, then let it cool down completely before removing the radiator cap!
These are the test steps:
- 1
Remove the radiator cap from the radiator.
- 2
Check the coolant level and add water if necessary.
- 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 up and out of the now open radiator.
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 bubbled out or shot out from the radiator as the engine was cranked. This result confirms that the head gasket is blown.
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, your next step is: TEST 3: Engine Compression Test.
If the engine starts and runs but overheats, your next test is: TEST 4: Using A Chemical Block Tester (Combustion Leak Tester).
