A few Buick owners (including members here) report a literal meltdown of the OEM plastic intake plenum assembly.

That plastic valve cover housing contains the Exhaust Gas Recycle line (EGR).

For some reason, the EGR line becomes overheated, melts the housing, and allows coolant and oil to mix. Repairs are expensive.

Obviously, that hazard should concern every owner of the GM engines which are at risk.

Now, I would like anyone who has had this problem to describe how they first noticed something was wrong, and any ideas they have about preventing that malfunction in the future.

My post is an effort to be proactive, and to prevent the problem before it occurs. Your experience and information will go far in helping other Buick owners who face the same hazard.

I appreciate the effort, but I'm sorry to say it'* kind of late.

This issue was found in many 3800 Series 2 naturally aspirated V-6 engines. These engines were installed from model year 1996 through 2003. The supercharged 3800 Series 2 did not have the issue, nor did the Series 1 and Series 3 3800'*. The newest ones to have this issue are over 20 years old and most have gone off to the great golf course in the sky. These would not show a sign of any evidence of issues on the outside.

There were some efforts to start class action suits for the poorly-designed plastic upper intake manifold. I don't recall any of them being successful.

The initial symptoms are usually one or more of three things:
- Slow coolant loss with no leaks
- Hydrolocked engine
- Steam in exhaust

My 1997 LeSabre had this issue, at around 145,000 miles. Got the upper intake replaced and am still driving it today with over 257,000 miles on it. I've heard of some having it happen with much less mileage, and many with much more. This easily lasted well out of warranty for most that it happened to, but it is still widely viewed as a flaw that was handled poorly by GM. For a company that built millions of cars that went to their grave with the original intake manifold still in place from the factory, both before the NA 3800 Series 2 and after it, most owners with an opinion on this feel this should have been a recall.

Since you described "a literal meltdown of the OEM plastic intake plenum assembly", it is probably important to address an issue that was not caused by the plastic upper intake manifold. The fuel pressure regulator in the naturally aspirated 3800 Series 2 would sometimes fail in such a way that engine vacuum would draw pressurized gasoline into the upper intake manifold. If anything ignited this gasoline, it would create an underhood fire, and occasionally a notable explosion. This was not a direct failure of the plastic upper intake manifold, but rather, was a failure of the vacuum operated fuel pressure regulator.

Moved from the "Buick" section to the "General GM Chat" section as this affects vehicles from Buick, Chevrolet, Oldsmobile, and Pontiac.

I have to believe there is not one of these engines around that has not already experienced this issue.
To be proactive would require the ability to go back in time.

There might be a few around that have been parked in garages all these years and haven't been used enough. Maybe three. Or four.

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Since this car is my primary transportation, I must take a reasonable, pro-active stance, and do what I can to repair and replace, as needed. In regard to the vacuum-driven fuel pressure regulator, is replacement possible?

You have confirmed in detail (much appreciated) all my other concerns about buying and installing the Dorman replacement full intake plenum. Interesintgly, in separate calls to Dorman approximately eight months apart, I got two answers to my question, "How does the Dorman part improve the OEM plastic manifold?" The first answer was a sales presentation of the Dorman part as a remedy for the OEM part vulnerability, in which the EGR line was further isolated from the plastic manifold housing by a special structure (unspecified). The second and later answer was a complete denial of any OEM intake plenum issue, or a special Dorman "remedy". In fact, I had to extract the information needed by the question, "How does the Dorman part differ-- if at all-- from the OEM part?"At that point, the Dorman parts specialist said the intake line has been modified with two sizes of aluminum intake line, each about 2-3 inches long. That metal line is believed to improve the durability of the part and help prevent problems.

As you have indicated, my attention must include the fuel pressure regulator-- hope it is still available..

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Frankly, I cannot thank you enough for that information.
In the past 24 hours, I have located fuel pressure regulator (new) at PartsGeek.com, and it appears user-installable.
Please let me know if you have further suggestions for similar preventive maintenance.

Yeah, it'* easy. Usually a five minute job if nothing breaks.

I can't speak for what they're doing today, but I do believe all of the reputable names are putting a metal sleeve in that EGR passage.

For what it'* worth, you can look on yours to see if the plenum that is on it now is a replacement or not. The production date codes are molded in the top. If this is your 1998 LeSabre (from your profile) that we're talking about, if the date shows 1999 or later, it is pretty much guaranteed to be a replacement and therefore possibly improved.

There are a bunch available everywhere. It helps that the same part was used on lots of different engines across three major manufacturers (GM, Honda, and Isuzu). I recommend the Delphi FP10016 that seems to be running around $50.00 right now.

Glad I could help!

I suggest this is not something to go cheap on. The Delphi FP10016 is a good unit.

Additional maintenance needs depend on the condition of the vehicle, how many miles are on it, what maintenance has been done in the past, and how long (in miles and time) you plan to keep it. Throw some details at us and we can come up with some answers for you.

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Understood-- my preference is Delphi and Delco/Remy, also, whenever possible
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VIN -- 1G4HP52K5WH500185
Buick 98 LeSabre Custom
Odometer 253,000
I am the third owner of this car, and until the immediately previous owner succumbed to his current wife, he had maintained good maintenance records. The aforementioned wife came upon the pile of his old Buick 98 maintenance records,and simply threw them out. That leaves me with an interesting voyage of discovery ahead.
Current projects include--
> replacinig the entire front brake assembly-- rotors, calipers and pads
> replacing the entire rear drum assembly
> replacing the EGR valve (the current EGR valve is still attached to its wiring harness, but nuts have been removed and the unit inverted, to leave it soaking in brake cleaner).
> replacing spark plugs and spark plug wires with a set rated for at least 100,000 miles
> preserving and protecting rubber and plastic body items, with UV-resistant products applied to surface
> inspecting suspension and steering parts and CV joints
Last fall, I replaced the battery and alternator, and plan periodic load checks and alternator output tests.
Plan to monitor oil consumption, as well as coolant, brake fluid and ATF levels.

Do you recommend I pull the transmission pan and filter and drain the fluid? No weird smells from the ATF, as of yet, and the pull-and-drain procedure may have been done more or less regularly by the next-to-previous owner.
I appreciate your interest!