How To Test For A Blown Head Gasket (2002-2009 4.7L V8 Dodge Ram Pickup)

If you suspect that you have a blown head gasket on your hands, then this tutorial will show you the three most common tests done to check for a blown head gasket.

A blown head gasket is the result of one of two things:

• Severe overheating.
• Hot spots on the engine deck or cylinder head surface (created by a leaking cooling system that does not pressurize), that burned the head gasket.

The end result is either a vehicle that starts and runs yet overheats or a vehicle that cranks but does not start. To get into more specific symptoms of a blown head gasket, let's jump into the next subheading.

You can find this tutorial in Spanish here: Cómo Probar El Empaque De Cabeza (4.7L Dodge) (at: autotecnico-online.com).

ENGINE NO-START DIAGNOSTICS:

• How To Test An Engine No-Start (2002-2009 4.7L V8 Dodge Ram Pickup).

Symptoms Of A Blown Head Gasket

The most common symptoms a blown head gasket are:

1. White smoke coming out of the tail-pipe when the engine is running.
   • This smoke has a very sweet smell to it (it's coolant cooking in the exhaust).
2. The engine in your 4.7L equipped Dodge or Jeep 'Cranks but Won't Start'. You have verified that:
   • Ignition system is OK (since you have spark coming out at all of the ignition coils).
   • Fuel pump is OK (you have verified that the fuel pump is delivering fuel to the fuel injectors).
   • All fuel injectors are injecting fuel.
3. Engine is overheating. You have checked that:
   • The fan clutch is good.
   • Thermostat is good.
   • There are no coolant leaks.
4. The engine oil is thick and tan to off-white color (mixed with coolant).

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.

TEST 1: Engine Oil The Color Of 'Coffee With Too Much Creamer'

There are three tests in this article, and chances are that you'll probably not have to do all three. Why? Well, because if the first or second test confirms you have a blown head gasket on your 4.7L Jeep or Dodge SUV or pickup, there's no need to do the third (the 3rd test is an engine compression test).

Before you start your troubleshooting, take a look at the entire article. The first two tests should take you less than 5 minutes to do.

OK, on with show, this is what you need to do:

1. 1

   Open the hood.

2. 2

   Pull out the engine's oil dipstick.

3. 3

   Check the color of the engine oil and its viscosity.

4. 4

   What you're looking for is:
   
   1.) The engine oil (sticking to the dipstick) is a color like 'coffee with too much creamer'.
   
   2.) The engine oil's color is normal.

OK, let's go into a deeper explanation of what these two results mean:

CASE 1: The engine oil looks like 'coffee with too much creamer'. This tells you that one (or both) of the head gaskets is history. You're gonna' have replace both head gaskets.

CASE 2: The color of the engine oil is normal. This is the correct and expected test result.

The next step is to go to: TEST 2: Compression/Exhaust Gases Shooting Out Of The Radiator.

Here's why: This is always the very first test that most automotive mechanics or technicians do to easily diagnose a blown head gasket, even we (or they) know that a blown head gasket doesn't always result in oil mixing with the coolant. Thankfully, there are more easy and simple tests to continue checking for a blown head gasket.

TEST 2: Compression/Exhaust Gases Shooting Out Of The Radiator

The second most common test, to see if the head gasket is blown or not, is to check if engine compression and/or combustion gases are escaping thru' the cooling system. This is another very easy test and does not require any tools whatsoever to do.

IMPORTANT: This test has to be done with a completely cold engine or you run the risk of getting scalded by hot coolant. If the engine in your 4.7L Dodge or Jeep vehicle starts and runs and has been running for any length of time, let the engine cool down completely before doing this test.

OK, here are the test steps:

1. 1

   Remove the radiator's cap from the radiator.

2. 2

   Check the coolant level, since the radiator has to be full of coolant for this test to work.
   
   If empty, add some water or coolant to bring the coolant level to full.

3. 3

   Have a helper crank the engine while you stand at a safe distance from the open radiator.

4. 4

   You'll see one of two results:
   
   1.) Either the water or coolant inside the radiator will shoot up and out of the now open radiator.
   
   2.) Or 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.

OK, now that the testing part is done, let's take a look at what your results mean:

CASE 1: The coolant shot out from the radiator as you cranked the engine. This is bad news and this let's you know beyond a shadow of a doubt that the head gasket or head gaskets are blown. No further testing is required.

CASE 2: The coolant DID NOT shoot out from the radiator as you cranked the engine. So far so good, but one more test is needed to make absolutely sure the head gasket is OK.

If the engine starts and runs with two cylinder misfires, go to: TEST 3: Compression Test.

If the engine starts, runs, but overheats within minutes for no apparent reason, go to: TEST 4: Using A Chemical Block Tester (Combustion Leak Tester).

TEST 3: Compression Test

It doesn't happen very often, but every now and then, the head gasket from one cylinder head burns in a spot between 2 adjacent cylinders.

When this happens in your 4.7L V8 engine, you'll see one of these two symptoms:

1. Cranks but does not start.
2. The engine runs with a misfire and you have two misfire codes registering in the PCM's memory.
   • These two misfire codes accuse side-by-side cylinders from the same bank.

If this condition exists on your vehicle's engine, the compression/combustion of one cylinder will leak into the other and vice-versa as the engine cranks and/or runs (and the compression pressure will be 0 PSI for both of the affected cylinders). The best way to confirm this is with a compression test.

OK, here's what you need to do:

1. 1

   Remove the spark plugs (you don't have to test all 8 cylinders).
   
   NOTE: If you know which 2 cylinders are the dead ones (on the same bank), you can test the compression of just those 2.

2. 2

   Disable the fuel system.
   
   You can accomplish this by unplugging the fuel injectors' connectors. Or by removing the ASD (Auto Shutdown) Relay.

3. 3

   Install the compression tester.
   
   Thread in the compression tester by hand, on the first spark plug hole you're gonna' start with.
   
   NOTE: 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. 4

   Have a helper crank the engine as you observe the compression tester.
   
   NOTE: Be careful when working around a cranking engine.

5. 5

   Crank the engine till the needle on the compression tester stops climbing.

6. 6

   Test the next cylinder.
   
   Crank the engine till the needle on the compression tester stops climbing.

If the head gasket is burned at a location between 2 cylinders, your compression tester will read 0 PSI for those two adjacent cylinders (on the same bank of cylinders) and the other 6 will have good compression readings. Let me give you a more specific example:

Let's say that I tested my 4.7L Dodge and I got the following compression tester readings:

• Cylinder #1 = 165 PSI
• Cylinder #2 = 180 PSI
• Cylinder #3 = 0 PSI (bad)
• Cylinder #4 = 170 PSI
• Cylinder #5 = 0 PSI (bad)
• Cylinder #6 = 170 PSI
• Cylinder #7 = 175 PSI
• Cylinder #8 = 170 PSI

The compression readings for cylinders #3 and #5 would be a dead giveaway that the head gasket got fried between those two cylinders because both of these cylinders belong to the same bank of cylinders.

Now, you may not see those exact same cylinders with 0 PSI readings. It may be #1 and #3 or it may be #4 and #6. The key here, is that whatever cylinders are affected, two of them will have 0 PSI compression and they will be both be side by side and on the same bank.

Let's take a look at your test results:

CASE 1: All cylinder compression readings where normal. These compression gauge readings confirm that the head gasket is OK and not burned at a point between two cylinders.

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'll need to replace the head gasket.

In case you do have a blown head gasket on your hands, you may be wondering:

1. How can I tell if the cylinder head is cracked?
2. How can I find out if the cylinder head is warped?
3. Do I need to resurface the cylinder head?
4. Do I need to remove both cylinder heads?

You can find the answers to the above questions here: Frequently Asked Questions.

TEST 4: Using A Chemical Block Tester (Combustion Leak Tester)

Every now and then, a blown head gasket on your 4.7L Dodge won't show any of the previous symptoms the previous 3 tests are trying to confirm. In a situation like this, the only way to make absolutely sure the head gasket is blown is by doing a chemical block test.

The combustion leak tester (or block tester) test is used in all major/competent repair shops to confirm a blown head gasket issue. In a nutshell this is how the test works:

• A blue liquid chemical, which is blue in color, is placed in the tester (see photo above).
• The tester assembly is then placed on the open radiator neck (you may have to drain some of the coolant in the radiator since this tool needs to 'gulp' some of the air inside the radiator).
• The rubber bellow is then squeezed to suck in the air up through the two fluid-filled chambers. As the air bubbles up through the fluid, it will cause a chemical reaction.
• If the blue chemical turns yellow (for gasoline engines), combustion gases are entering the radiator. This result confirms a head gasket failure, a cracked block, or a cracked cylinder head issue.
• If the blue chemical doesn't change color, you can conclude that you don't have a head gasket failure, a cracked block, or a cracked cylinder head issue.

Where can you get the chemical and block tester? You can buy it here:

Disclosure: As an Amazon Associate, I earn from qualifying purchases. Buying through these links helps support this site at no extra cost to you. I truly appreciate it!

Frequently Asked Questions

1.)  How can I tell if the cylinder head is cracked?

The cylinder head has to be removed and visually inspected. If the crack is wide enough, you'll be able to easily see it.

Sometimes, a visual inspection proves inconclusive, this is why it's important to let a machine shop pressure test it for you.

2.)  Do I need to resurface the cylinder head?

YES, you need to resurface the cylinder head! You should never reinstall the cylinder head or cylinder heads without first having a Machine Shop resurface the cylinders heads (particularly over an overheating condition).

Now, of course, if you (or the machine) have checked it with a straight-edge and there's no warpage, then and only then is the cylinder head not resurfaced.

3.)  Should I remove both cylinder heads?

YES, you should remove them both to visually inspect them both and/or have a machine shop test them for warpage and cracks.

More 4.7L Dodge Tutorials

You can find a complete list of tutorials in this index:

• 4.7L V8 Dodge Ram Pickup Index Of Articles.

Here's a small sample of the 4.7L Dodge tutorials you'll find in the index:

• How To Test The COP Ignition Coils (2002-2007 4.7L V8 Dodge Ram Pickup).
• How To Test The Fuel Injectors (2002-2009 4.7L V8 Dodge Ram Pickup).
• How To Test The CKP Sensor -P0320, P0335, P0339 (2002-2010 4.7L V8 Dodge Ram Pickup).
• How To Troubleshoot A Cylinder Misfire -P0300↔P0308 (2002-2009 4.7L V8 Dodge Ram Pickup).