How to fix 3.8L Coolant Leak

2002 Pontiac Grand Prix with 3.8L Series II SFI OHV V6

Well known issue with these. The Upper Intake Manifold Gasket melts in close proximity to the EGR stove pipe allowing coolant and oil to get in bad places. My upper was leaking, but the Lower Intake Manifold Gaskets were a mess!

Click on pic to get a closer look. Yikes!

For about a month, it was eating antifreeze. I kept topping it off, until the inevitable, it overheated. Water started pouring from broken Upper and Lower Heater Bypass Pipes (Identify this leak) (Fix this leak) and oil mixed with the antifreeze through the intake gaskets. For the first time, it was now running rough. Feared the worst.

After a good compression check, I replaced all the gaskets from the lower intake manifold on up, the water pump, plugs and wires. Fired right up! All good! AHOO!

Redesigned Lower Intake Gasket Set from GM 89017816 ($65 dealer)

Improved Design Upper Intake Manifold and Gaskets from Dorman 615-180 ($130 autozone)
Dorman Heater Pipes 47065 ($5 autozone)
Heater Adapter O-Rings 24502375 ($10 dealer)

Redesigned gasket is now aluminum with molded seal

Disconnect the wire harness from the ICM before running a compression check!
To replace the water pump, you must remove the power steering pump. Not the PS pulley! (Video)
Do not use Carburator Cleaner on the throttle body and Emission Sensors! They make special cleaners for throttle body and MAF Sensor.
Wish I had used a little Permatex on the Heater Pipe O-Rings. They weep a little.
The upper and lower gaskets go on without dressing! Just a dab of Gasket maker in the corners of the lower (above and below).
The UIM comes with a new vacuum port and o-ring, but it felt loose to me. I added the old o-ring to the upper shoulder to snug it up to the manifold.
Step by Step help at

Very happy with this fix. About 75 people read this post every day. Give me some feed back! Did I help?


14 thoughts on “How to fix 3.8L Coolant Leak

  1. I’m working on finishing putting intake manifold on I may just buy new one instead of using old one it’s caked with oil it was really bad no cracked head but still was only running on 2 cylinders

  2. Do the dealers know about this and why won’t they tell you what it is and fix it. Most of us would get it fixed. What are they waiting for? For me to buy a new car down at the Ford Dealers. Thanks.

  3. my 2005 Impala SS has had this gurgling noise in the dash, first on the passenger side, now the passenger side toward the middle when i start the car on a cold mornng…pretty soon after going about a mile i wont hear it anymore. never has any water leaked on the floor or anywhere else. that’s been going on for about two months. took it to a shop early on and he said he vacuumed air out of the cooling lines. That’s what he said. Well, four days ago, i started the car, went about a foot and the low oil pressure light came on. I am a woman and sure dont know about this stuff but I am wondering could all this stuff be what you are talking about on your post or could it just be an oil sending unit, heater core…what. I dont even know if i should attempt to drive it to a shop or have it hauled in. I checked the oil and it’s fine. Does not appear to have any water in it, I have the oil changed religiously every 3000 miles. Oh, the heater works great, I have a habit of watching my guages also, no overheating, oil guage is fine…just gotta put that stupid high priced gas in the thing. Premuim only per the instruction manual. So, if you got any feedback on this, I would surely appreciate your advice.

    • I am no mechanic, but in my opinion, the gurgling was simply air in the cooling system. Bleeding or toping off the coolant should have resolved that. Low oil pressure is unrelated and must be addressed. Could be a bad oil pump. But you dont want to go far on low oil pressure. Get to a shop. If you had no oil pressure you would immediately hear unnussual tapping, banging sounds. That’s time to shut it off and call for a tow.

      • I have a 2004 Impala SS with 143,000 miles which has the same gurgling noise that you described and like your vehicle I didn’t notice any coolant under the vehicle, but did notice this past winter that the temperature was slow to come up to normal temperature and that I would get an occasional check engine light that would come and go. I thought that the check engine light was a different issue until I discovered that the light is being triggered by the engine not coming up to temperature within a set period of time. Bottom line is that my Impala is leaking coolant somewhere (I suspect the 90 degree coolant connectors) and causing the gurgling and check engine light. Have verified that by adding coolant to the plastic overflow bottle that both of these issues disappear for a while but the gurgling always returns. I have also discovered coolant at the bottom of the engine on the passengers side below these plastic 90 degree elbows. So will be taking things apart in the next few days to see if this is really where the leak is.
        So, this gurgling is air in the cooling system, but the issue is probably how did the air get there or where is the coolant leaking. As stated previously, the oil pressure is a separate issue.

      • Yes you are correct, I found that one of the plastic elbows was cracked on the outside of the O-ring. Then upon further inspection behind the supercharger I found a small pond of orange anti-freeze on the lower intake manifold. I ended up removing the alternator bracket, the injector rail, the wiring harnesses, the supercharger and the lower intake manifold to replace the gaskets. Just as stated in many of the blogs, the lower intake manifold gaskets were leaking coolant and oil. Anyway, to make a long story short, everything is back together and car is running significantly better and does not lose coolant. How many of the oil leaks were fixed is yet to be determined. This job was definitely one that takes some time, since every plastic vaccum fitting / hose broke / cracked the minute I touched them. Thus requiring that I had to fabricate something or make a trip to the GM dealer to order a part.

  4. I did my 2003 Olds Silhouette this summer. It began pissing coolant out the rear of the engine this winter. We lost heat on a road trip. Started overheating. We kept filling it, but with air in the system (not bled) it was a roller coaster ride of heat/no heat.

    I am an avid DIY, and a home mechanic since 6 with dad. I took it to a few shops, and even paid the dealer $90 for analysis. No one could give me a str8 answer. Its not rocket science fellas!

    You bet, I had every diagnosis. Plugged heater core, bad thermostat, head gasket, intake – either one and both, cracked heads- pure guesswork. The dealer that charged me $90 should have given me an answer, but nope.

    Weeks later I decided it was time to just do the job. 94,000 miles, dexcool mix with antifreeze etc, it “had” to be the issue. I bought the parts just like you and went to town. Its not as bad as the shops try to tell you, but its not a job one should do if you have not done one before. I had quotes (lowest @ $680, highest @ $3700).

    I got into the job (its now June) and the intakes looked fine, but the OEM semi-metallic head gasket was cracked, the rear head had a healthy groove “channel” eaten into it and that alone called for machining. This costs ~$80 a head, up to $120 each on average. I got both done for $120 took a few days. The exhaust studs can be a #$^& and were in mine, the shop was nice enough to dig them out for me, and even supplied new ones! BONUS!

    I’m rather meticulous and cleaned it like nuts which the shop didn’t do. I only wanted to do this job once. The intake gaskets on mine were pure plastic and were not in bad shape but I replaced everything while in there.

    Meticulously 16 hours later I was done, and the vehicle was good to go. I had to bleed it three times, but it runs well.

    The moral in my story, is that I found yours so close to home with 1 major difference…. You didn’t do the head gaskets. Considering the work involved in doing the lower intake, I would certainly argue that “if its not broke don’t fix it” does NOT apply in this situation and I would advise anyone doing this job (intakes), to go all the way.

    The gaskets often break down because of the breakdown and lack of maintenance on the DEXCOOL system and the head gasket being metallic succumbs to the acidic crud just as much, if not more than the intakes do.


    • Thought pretty long about doing the heads, too. After all, they are right there staring you in the face! I decided against it for a couple reasons. Before I started the job, I had good cylinder compression tests and felt pretty good. Also, I know the odds of breaking Exhuast Manifold studs. I really just didn’t want to open another can of worms… At that point, I just wanted to get it back together. I am just a shade tree mechanic. If I was still in my teens and didn’t need the car running right away, I probably would have gone for it.
      By the way, did you toss your Head bolts and get new? They are “torqued to yield”. Which means they are deformed by installation and should not be reused.

      • I have a 2004 Chevy Impala ls. I am a single mother with 2 kids and bought my impala in 2005 with 25,00mls. I NEVER had a problem until about year ago. I heard what sounded like water dumping out something on the passenger side. Than about 2 months later my car started over heating. I replaced the fuel pump, replaced hoses. My mechanic told me because the engine is cast iron it causes it to rust and that he fixed the hose but the car was always going to give me problems because of the cast iron engine. I drove it for 3 months and I over heated AGAIN!!! I also had a cloud of smoke coming out my exhaust. I brought it to a different mechanic and he said I blew a head gasket. I replaced the heads and gaskets. It ran for about a month and half before I noticed my transmission slipping and right after that it stating over heating AGAIN while I was driving and it killed. Oh I also changed the thermostate when I had the water pump changed. I am so lost. I can’t afford another car!!!! Can SOMEONE PLEASE HELP ME ???!!!!!!!

      • #1 never go back to the guy that said the car is always going to give you problems. He’s doesn’t want to help you.
        #2 go back to the guy that did the heads. your overheat problem should have been resolved there.
        #3 The transmission slip is a separate issue and should be handled by a trusted mechanic. It could be something simple.

  5. Pingback: Coolant Leak - Page 2 - 3.8L V6 Supercharged (L67)(L32)

Leave a Reply

Fill in your details below or click an icon to log in: Logo

You are commenting using your account. Log Out /  Change )

Google+ photo

You are commenting using your Google+ account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )


Connecting to %s