How To Test For A Blown Head Gasket (1993-1998 3.0L V6 Nissan Quest)

There are four tests you can perform on your 3.0L V6 Nissan Quest to find out if you've got a blown head gasket on your hands or not.

Two of these tests don't require any tools at all and can be done in under five minutes. The other two are a compression test —which requires a compression tester— and a block test, which requires a combustion leak detector.

All of the tests are explained in a step-by-step manner so you can quickly and easily figure out if a head gasket failure has happened on your Nissan Quest.

Hopefully you're not dealing with a blown head gasket, but if you are, this tutorial will help you find out for sure.

APPLIES TO: This tutorial applies to the following vehicles:

• 3.0L V6 Nissan Quest: 1993, 1994, 1995, 1996, 1997, 1998.
• 3.0L V6 Mercury Villager: 1993, 1994, 1995, 1996, 1997, 1998.

Symptoms Of A Blown Head Gasket

In most cases, a blown head gasket is the direct result of the engine severely overheating. And when one or both head gaskets have failed on your Nissan Quest, you're going to see one or more of the following symptoms:

• Overheating: The engine runs hot, and you can't find an obvious reason for it.
• Oil and coolant mixing: The oil turns a milky color —looks like coffee with way too much creamer— from coolant leaking into the crankcase.
• White exhaust smoke: Thick, white smoke coming out of the tailpipe from antifreeze burning inside the cylinders.
• No-start condition: The engine will crank, but it just won't fire up.
• Cooling system overpressure: The coolant expansion tank gets overpressurized and starts pushing coolant out whenever the engine idles or after you shut it off.

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

You're probably already aware that coolant is circulated through the engine block and then through the cylinder heads on its way to the radiator. The head gaskets —and your Nissan Quest has two— are designed to keep coolant, engine oil, and what happens in the combustion chambers separated.

When a head gasket fails, it loses this ability to keep everything separated. And when that happens, you'll usually see the engine oil mixed with coolant, making it look like coffee with way too much creamer.

We can easily check to see if this has happened on your Nissan Quest by simply pulling out the dipstick and looking at the condition of the engine oil on it.

If the oil has a milky-white color —like coffee with way too much creamer— then you've confirmed that one or both head gaskets have failed. If the engine oil looks its normal color, we'll move on to TEST 2.

Alright, let's get to it:

1. 1

   Open the hood.

2. 2

   Pull out the engine's oil dipstick.

3. 3

   Check the color of the oil.

4. 4

   You'll see one of two things:
   
   1.) The engine oil will be a creamy tan/off white color and as thick as syrup.
   
   2.) The engine oil will be a normal color and viscosity.

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

CASE 1: The engine oil is a milky white color, like coffee with too much creamer. This confirms that you do have a blown head gasket issue on your hands. You'll need to replace both cylinder head gaskets.

CASE 2: The engine oil color is normal. So far, so good. We now need to move on to the next test, which is checking to see if exhaust compression pressures are escaping into the engine's cooling system. Head over to: TEST 2: Exhaust Gases Shooting Out Of The Coolant Expansion Tank.

TEST 2: Exhaust Gases Shooting Out Of The Coolant Expansion Tank

As the engine is cranking or running, each cylinder goes through a combustion cycle that creates several pressures —compression, combustion, and exhaust. When the head gaskets are in good shape and doing their job, they keep those pressures sealed inside the cylinders and prevent them from entering the engine's cooling system.

If one or both head gaskets have failed, that seal is usually lost. Now you've got combustion gases escaping into the coolant passages in the engine block and entering the cooling system.

You and I can easily check for this condition by cranking the engine with the radiator cap removed. We can expect one of two results from this test:

• Coolant remains undisturbed in the radiator: This is the correct and expected test result.
• Coolant gets shot out forcefully from the radiator: This confirms that one or both head gaskets have failed and are allowing combustion pressures into the engine's cooling system.

CAUTION: This test must be done with a completely cool or cold engine. If your Nissan Quest's engine has been running for any length of time, let it cool down completely before removing the radiator cap. Opening a hot radiator can cause serious burns from escaping coolant. If you need to speed up the cooling process, place a fan over the engine to help it cool faster.

Here's what to do:

1. 1

   Take off the cap from the coolant expansion tank.
   
   Make sure the tank has enough coolant. If it's low or empty, add water or coolant until it reaches the proper level.

2. 2

   Have your helper crank the engine while you watch the coolant level from a safe distance.

3. 3

   You'll get one of two results:
   
   1.) The coolant inside the expansion tank shoots up or bubbles out.
   
   2.) The coolant level remains undisturbed —cranking the engine has no effect.

Here's how to read the results:

CASE 1: The coolant bubbled up or shot out while cranking the engine. This is not good, since this test result confirms that one or both head gaskets on your 3.0L V6 Nissan Quest have failed.

CASE 2: The coolant remained undisturbed as you cranked the engine. This is the result we want to see. It confirms that the head gaskets are not allowing combustion pressures into the engine's cooling system. Now, we're not out of the woods yet —the next step depends on what the engine does once it starts.

Choose one of the following:

• If the engine starts, runs, but suffers a cylinder misfire —go to: TEST 3: Doing A Compression Test.
• If the engine starts, runs, but overheats within minutes —go to: TEST 4: Using A Chemical Block Tester (Combustion Leak Tester).

TEST 3: Doing A Compression Test

In some cases, one of the head gaskets on your 3.0L V6 Nissan Quest will fail at a spot right between two side-by-side cylinders. When this happens, the engine will start and run, but it'll run with two dead cylinders —and it's going to shake quite a bit because of it.

If you take a look at the photo of the blown head gasket at the beginning of this tutorial, you'll see exactly this type of failure, where the gasket has burned through right between two adjacent cylinders.

To pinpoint this type of head gasket failure, we need to do an engine compression test. In the results, we're specifically looking for two side-by-side cylinders that both show zero PSI compression.

NOTE: You can find a more complete and detailed explanation of how to do a compression test on your Nissan Quest in this step-by-step tutorial: How To Do And Interpret An Engine Compression Test (1993-1998 3.0L V6 Nissan Quest).

OK, here's what you need to do:

1. 1

   Disable the ignition system.
   
   You can easily accomplish this disconnecting the ignition coil's electrical connector (if your vehicle has a distributor) or the ignition coil pack's electrical connector.

2. 2

   Disable the fuel system. It's important that fuel not be injected into the engine.
   
   You can do this by removing the fuel pump relay or the fuel pump fuse.

3. 3

   Disconnect all spark plug wires (from their spark plugs) and then take out all of the spark plugs.
   
   NOTE: Before you remove the spark plug wires, label them so that you'll be able to easily reconnect them to their proper original locations.

4. 4

   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.

5. 5

   Have a helper crank the engine while you observe the compression tester.

6. 6

   Once the gauge's needle stops climbing, have your assistant stop cranking the engine.

7. 7

   Write down the reading and what cylinder it belongs to (you can use the image in the image viewer to help you identify the cylinder) on a piece of paper.

8. 8

   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 similar. These compression gauge readings confirm that the head gaskets are OK and not burned at a point between two cylinders.

If you still suspect that you've got a blown head gasket on your hands, especially if the engine overheated recently, your next step is to do a block test with a combustion leak detector. 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'll need to replace both head gaskets.

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

One of the go-to tests performed at repair shops when troubleshooting a cylinder head gasket issue —especially when the oil looks normal and coolant isn't being shot out of the radiator while cranking the engine— is using a combustion leak detector to see if one or both head gaskets are in the early stages of failure.

At this point, you're not seeing these failures wreak havoc on engine performance, but you will see the engine overheating within minutes and apparently for no reason. In these tough-to-diagnose cases, the block tester will definitely save the day.

You'll need to buy or borrow a block tester (you can borrow one from AutoZone or O'Reilly Auto Parts), but this tool will give you a solid, accurate answer.

In a nutshell, here's how the block tester works:

• A blue chemical solution is poured into the tester (see photo above).
• The tester is set on the open expansion tank neck. You may have to drain a little coolant to let the tool pull in radiator air.
• Start the engine.
• Squeeze the rubber bulb to draw air through the fluid chambers. The bubbling air reacts with the chemical.
• If the fluid changes from blue to yellow (on gasoline engines), combustion gases are present in the engine's cooling system. That means a blown head gasket, cracked block, or cracked cylinder head.
• If the fluid stays blue, then those issues are not present.

You can get the chemical and block tester at most auto parts stores or here:

Frequently Asked Questions

1. Do I need to remove both cylinder heads? Yes. Once you've confirmed that you do have a blown head gasket, both gaskets need to be replaced. And while both cylinder heads are off, they should each be checked for cracks and warpage.

2. How can I tell if the cylinder heads are cracked? Once the heads are removed, you can flip them over and look for any visible cracks. If a crack is large enough, you'll spot it easily. But most of the time, checking for cracks should be done by a machine shop using a pressure test to confirm that both heads are OK.

3. Do I need to resurface the cylinder heads? Yes —you should absolutely have a machine shop resurface the cylinder heads if they're still within the allowable material-removal limit. The machine shop will let you know whether each head can be resurfaced or not.

Now, depending on what you're doing, you can also check for warpage yourself with a straightedge. If the head isn't warped —and especially if the engine did not overheat— then you may not need to resurface it. The key here is confirming (with a straightedge) that the cylinder head–to–block mating surface is flat, and that the engine hasn't suffered an overheating condition.

4. Do I need to replace the cylinder head bolts? Yes. The head bolts on your Nissan Quest are torque-to-yield bolts. As they're being torqued, they're turned a specific number of degrees, and when this happens, each bolt is designed to stretch. So if you reuse the old head bolts, you're reinstalling bolts that have already been stretched and weakened —and that's a recipe for a nightmare.

When reinstalling the cylinder heads, be sure to use new head bolts.

More 3.0L V6 Nissan Quest Diagnostic Tutorials

You can find a complete list of 3.0L V6 Nissan Quest diagnostic tutorials in this index:

• 3.0L V6 Nissan Quest Index Of Articles.

Here are some of the tutorials you'll find in the index:

• How To Test The Ignition Coil And Power Transistor (1993-1998 3.0L V6 Nissan Quest).
• How To Test The Camshaft Position Sensor (1993-1998 3.0L V6 Nissan Quest).
• Common Causes Of Spark Plug Failure (1993-1998 3.0L V6 Nissan Quest).
• How To Do And Interpret An Engine Compression Test (1993-1998 3.0L V6 Nissan Quest).