Found this great article at troubleshootmyvehicle.com(link):

If you suspect that your 3.8L GM vehicle (whether it’s a Buick, a Chevy, a Pontiac, or an Olds) has a Blown Head Gasket and don’t know how to test this... well, you’ve found the right article. I’m gonna’ show you how to do three of the most common tests to verify a Blown Head Gasket.

All three tests are explained in a step-by-step fashion and more importantly... I’ll explain the test results that you’ll obtain from the tests.

To make it easier to navigate this article, here are its contents at a quick glance:

  • HEAD GASKET TEST 1.
  • HEAD GASKET TEST 2.
  • HEAD GASKET TEST 3.
  • Symptoms of a Blown Head Gasket.
  • Related Test Articles.

HEAD GASKET TEST 1:

The first two tests are the fastest and the easiest to do and they are very accurate too. The first test or the second may be enough to verify that the Head Gasket is Blown on your GM 3.8L equipped car or mini-van, so there’s a good possibility that you may not have to do all three. So, before you start on this first test... take a look at the whole article.

Alright, this test should take you less than 2 minutes to do:

  1. 1

    Pop the hood on your 3.8L GM car or mini-van and once open, check the Engine Oil by pulling out the Engine’s Oil Dipstick.

  2. 2

    The idea behind this test is to see if Coolant is mixing with the Engine Oil and so you’ll notice one of two things:

    1.) Either the color of the Engine Oil will be an off-white/tan color 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 Engine Oil is an off-white/tan color, and your car or mini-van overheats and/or doesn’t start... this confirms that your vehicle has a Blown Head Gasket.

Why does the oil look like this? Mainly because your 3.8L GM car or mini-van over-heated and :

1.) The Cylinder Head (or Heads) warped and one of the two Head Gaskets on your 3.8L engine burned.

2.) Once one of the two Head Gaskets on your engine burns, it won’t be able to keep the Engine Oil or Coolant separated...

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, so far so good, but if your vehicle is still overheating (and you’ve verified that the Thermostat and Cooling Fans are OK)... you’ll need to do two more tests. Go to HEAD GASKET TEST 2.

Here’s why: In most cases, when one of the Head Gaskets burns on a 3.8L GM car or mini-van, the Coolant does mix with the Engine Oil. But not always, and so then, there’s the need to do some more tests. The next test is to see if the Engine Compression and Exhaust Gases are escaping thru’ the Cooling System (specifically the Radiator).

HEAD GASKET TEST 2

The second most common test, to see if the Head Gasket on your 3.8L GM car or mini-van 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.

Now, before you start... if the engine has been running for an extended amount of time and it’s hot, let the engine cool down for at least 1 hour. This is important, or you run the risk of getting scalded with hot Coolant.

If your 3.8L GM car or mini-van doesn’t Start, well this is not an issue. OK, here are the test steps:

  1. 1

    Remove your pick up or car’s Radiator’s Cap. 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.

  2. 2

    Now, get your helper to crank the engine, while you stand at a safe distance from the open Radiator.

  3. 3

    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.

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

CASE 1  The Coolant bubbled out or shot out from the Radiator: This is bad news and this let’s you know beyond a shadow of a doubt that the Head Gasket on your 3.8L GM car or mini-van is blown. No further testing is required.

CASE 2  The Coolant DID NOT bubble out NOR shoot out from the Radiator: So far so good, but one more test is needed to make absolutely sure the Head Gasket is OK, go to HEAD GASKET TEST 3

Now, common sense tells you that if a Head Gasket is Blown... you ARE gonna’ have Oil mixed with Coolant, and Engine Compression and/or Combustion Gases are going to be shooting out of the Radiator... but sometimes this just doesn’t happen. So, the next test will further confirm or exonerate the Head Gasket.

HEAD GASKET TEST 3

One of the most overlooked tests, to see if the Head Gasket is BAD or not, is an Engine Compression Test. Why? Well because most folks will do the two previous tests (HEAD GASKET TEST 1 and HEAD GASKET TEST 2) and they will not see the Engine Oil mixing with the Coolant nor see the Combustion Gases jumping out of the open Radiator and conclude everything is OK. And whatever information they have available never mentions testing the Engine Compression.

Well, now you know that it is possible for the Head Gasket to burn and not cause the Oil to mix with Coolant nor cause the Exhaust Gases to escape thru’ the Cooling System. In this test step, you’ll be doing a Compression Test and more importantly... you’ll be able to easily interpret those results (with my help) to further confirm or exonerate a Blown Head Gasket.

This test will see if the Head Gasket on your 3.8L GM car or mini-van has burned at a point between cylinders.

If this does happen, the Compression/ Combustion of one cylinder to leak into the other and vice-versa and the Compression readings will easily let us know this has happened.

OK, here’s what you need to do:

  1. 1

    Disable the Fuel System and the Ignition System. It’s important that Fuel not be injected into the engine and Spark not be delivered to the Spark Plug Wires.

    You can do this by disconnecting Ignition Control Module’s electrical connector (this will disable both Systems).

  2. 2

    Disconnect all Spark Plug Wires (from their Spark Plugs) and then take out all of the Spark Plugs. I suggest you label all of the Spark Plug Wires before you unplug them from the Spark Plugs, that way you’ll know where they go when you’re done.

  3. 3

    Thread in the Compression Tester by hand, on the first Spark Plug hole you’re gonna’s 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.

  4. 4

    Have a helper crank the engine. Your job is to observe the Compression Tester.

    This is what is gonna’ happen: The Compression Tester’s needle will climb, as the engine cranks, till it reaches the maximum Cylinder Compression. At the point it stops climbing, have your assistant stop cranking the engine.

    Now, 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. Remove the Compression Tester and repeat the above steps in the remaining cylinders.

OK, before I jump into the above Compression Test result interpretations, let me give you some more detailed information as to what you’re trying to accomplish with this test... If the Head Gasket is burned at a location between 2 Cylinders... your Compression Test readings will give you 2 good compression readings and 2 Compression readings that will be 0 PSI. Let me give you a more specific example:

Let’s say that I tested my 3.8L GM car or mini-van and I got the following Compression Tester readings:

  • Cylinder #1 = 165 PSI
  • Cylinder #2 = 180 PSI
  • Cylinder #3 = 0 PSI
  • Cylinder #4 = 170 PSI
  • Cylinder #5 = 0 PSI
  • Cylinder #6 = 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. Now, in your 3.8L GM car or mini-van... 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.

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.

OK, 3 out of 3 tests have confirmed that the Head Gasket on your 3.8L GM car or mini-van is not blown.

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 will need to replace the Head Gasket.

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. 1

    Your 3.8L GM car or mini-van is overheating. You know it’s not the Fan (or Fan Clutch) or Thermostat.

  2. 2

    White Smoke is coming out of the tail-pipe and it smells like Anti-Freeze being cooked.

  3. 3

    Your 3.8L GM car or mini-van 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. 4

    The Engine Oil is thick and tan to off-white color (mixed with Coolant).

Related Test Articles

There are several more 3.8L GM car or mini-van specific ‘How to Test’ articles that I’ve written for your troubleshooting and diagnostic benefit. The articles that are here in this Web Site... you can find them here: GM 3.8L Index of Articles.

At easyautodiagnostics.com, you’ll find the following articles:

Reader's Real Life Case Studies and Solutions

In this section is input and feedback from all of the folks who have had a similar issue with their vehicle and found a solution. If you're one of them, I want to thank you for sharing your experience with all of us!

If you want to share your repair and/or diagnostic experience, you can use the contact form below.

Real Life Case Study 1

Vehicle: 2000 Buick Park Ave. (Base) 3.8L V-6, 172,000 miles

Trouble Codes: P0303 and P0304

Complaint: LOW COMPRESSION ON #3 AND #4 “...I lost a water pump going up a 6% grade incline at high speed and wasn't watching the temp. gauge. I used some Duraseal to overcome some coolant leak problems, but still had a 70 lb. compression reading on #3 and #4 and was throwing P0303 and P0304 codes...”

“...Another compression test gave the same results, and when we added a spoonful of oil (for a wet compression test) it only came up ten pounds, to about 80 psi. At that point, I figure that it may be a valve problem, a burnt seat or a bent valve, etc...”

Test Notes: “..The initial compression test indicated a problem and I wanted to believe a head gasket problem was the source of that loss of compression. But even after doing the chemical fix – which worked – I still had loss of compression. With the wet test showing little improvement, the inescapable conclusion was that the valves were compromised...”

“...At that point I looked at the cost of paying someone to tear it all down, then magnaflux the heads and fix the bad valves and put it all back together: not a small amount. The problem is that even once you do that, if you do that, you then have a strong upper engine working on a 170,000 lower engine. The prospect is that then – as many times it has been seen – that later the lower end is blown out and you have to start all over again to do a ring job. Tilt!...”

Repair: REPLACED ENGINE “..I called the S** V***** area salvage yards to find a low mileage used engine in the L*** area. The salvage yard gave me a price of $1,500 to buy the engine AND install it. He used my existing plastic Intake Manifold, not the metal one on the ‘new’ engine, and got it to work...”

Advice: “...That is the key thing I learned. IF YOU ARE LOSING COOLANT OVER TIME, CHECK THE WEEP HOLE ON YOUR WATER PUMP FIRST. That is the first place to look. If I had done that and replaced the water pump when it was telling me it was about to go, I would have avoided all the time and cost of the repairs I incurred. But now I am even better off, in a way, with a low mileage engine to go with my already rebuilt tranny... ”

Courtesy of: Dave Cramer

Notes: You can read Dave's entire post here: Dave's Post.

Oldsmobile Vehicles:

    Cutlass Ciera (& Cruiser) 3.8L
        1993
    Intrigue 3.8L
        1998, 1999
    LSS 3.8L
        1996, 1997, 1998, 1999
    Regency 3.8L
        1997, 1998
    Silhouette 3.8L
        1993, 1994, 1995

Oldsmobile Vehicles:

    88 (& 88 Royale) 3.8L
        1993, 1994, 1995, 1996, 1997, 1998
    98 Regency 3.8L
        1993, 1994, 1995, 1996
    Achieva 3.8L
        1993

Chevrolet Vehicles:

    Camaro 3.8L
        1995, 1996, 1997, 1998, 1999, 2000, 2001, 2002
    Impala 3.8L
        2000, 2001, 2002, 2003, 2004, 2005
    Lumina (& MPV)
        1993, 1994, 1995, 1998, 1999
    Monte Carlo 3.8L
        1998, 1999, 2000, 2001, 2002, 2003, 2004, 2005

Buick Vehicles:

    Regal 3.8L
        1993, 1994, 1995, 1996, 1997, 1998, 1999, 2000, 2001, 2002, 2003, 2004
    Riviera 3.8L
        1993, 1994, 1995, 1996, 1997, 1998, 1999
    Skylark 3.8L
        1993

Buick Vehicles:

    Century 3.8L
        1993
    LeSabre 3.8L
        1993, 1994, 1995, 1996, 1997, 1998, 1999, 2000, 2001, 2002, 2003, 2004, 2005
    Park Avenue (& Ultra) 3.8L
        1993, 1994, 1995, 1996, 1997, 1998, 1999, 2000, 2001, 2002, 2003, 2004, 2005

Pontiac Vehicles:

    Grand Prix 3.8L
        1997, 1998, 1999, 2000, 2001, 2002, 2003, 2004, 2005, 2006, 2007, 2008
    Trans Sport 3.8L
        1993, 1994, 1995

Pontiac Vehicles:

    Bonneville 3.8L
        1993, 1994, 1995, 1996, 1997, 1998, 1999, 2000, 2001, 2002, 2003, 2004, 2005
    Firebird 3.8L
        1995, 1996, 1997, 1998, 1999, 2000, 2001, 2002
    Grand Am 3.8L
        1993