12th Dec 2008, 05:36

OK, OK I have read all these comments and yes the same problems keeps occurring. I have also experienced this first hand with my 1995 Buick Park Ave. I replaced it myself with the "improved version" and its been fine for the last 10k miles. I agree with everyone that this a design flaw and GM should step up, but I can honestly say I love this car. I commute 200 miles per day to work and back. This is why I purchased this car. Who else makes a car this big and comfortable that gets 29 mpg on the highway.

Replacing the upper plenum is not that difficult. Takes a couple of hours and 100 bucks for parts. Then your car should be good for many more miles. A few people here are paying upwards of 1200 dollars for this job. These mechanics are getting rich off of GMs screw up.

If you do an internet search for 3.8 upper plenum there are tons of links about replacing it step by step and where to get the parts. It really is a pretty simple task that most of us can handle with a few hand tools and a free afternoon. Good luck guys.

PS- I'll be shopping for another Buick if I can ever wear this one completly out.

22nd Aug 2009, 15:35

Hi, I also have a 98 Buick Lesabre. I am having the same problems as others have mentioned. I went on break at work to find the car would barely start and when it did I could not see because of the "fog". That would be the smoke out of the tailpipe. Thanks a lot GM!!! You get what you put in!!!

5th Nov 2009, 16:03

I am having the same problem with coolant. I have a 98 LeSabre, it's losing coolant, but no sign of leaks. Does this mean the manifold has already failed? Is it too late for the adapter to mentioned in previously. Also how difficult is it to change the plastic upper manifold.

13th Dec 2009, 12:47

I have the same problems as all of the above, my car was fine until it stalled, but I was able to get it started and get it home! No signs of coolant leaks, but 4 out of 6 cyl. had coolant in them, the car has only 58000 on it. Plastic parts and metal don't work just like GM's plastic timing gears and metal chain???

14th Jan 2010, 01:15

98 LeSabre plastic manifold leaked and replaced years ago at about 70,000 miles. GM charges for the replacement part (imported from Mexico), and lacks the decency to at least provide the part. Didn't these parts fail in testing, or did the accountants view the customers as an expendable revenue source? They have worked hard to drive their most loyal customers to their competitors.

2nd Feb 2010, 10:16

I have a 1998 Buick Park Avenue with the same 3800-K series engine.

The manifold plenum collapsed, so the car stopped running. Thankfully it did not ruin the engine, as I was driving very slowly at the time it occurred. The dealer wanted like $700 or so to replace the plastic (!) manifold. I towed it home instead, and got online to research it. I ended up buying and installing little repair kit (today it's $70) and replaced it in about 4 hours. That was years ago, and the car is still operating very very well.

I recommend not replacing the plenum for so much money, and just buying a kit and installing it or finding someone who will install it for you (dealers won't do it, and most shops won't either because it's not a Buick factory part - like the PLASTIC parts they provide are acceptable?).

Anyway, it's a pretty simple job. The repair kit is made by Ken-Do Industries and is

Part #MR38K for 1995-2003 GM 3800 (K) Series

Plenum and Intake Repair Kit

Good luck!

My son and I are installing another kit in his newly purchased 1998 LeSabre this Saturday to make sure he doesn't have any problems with it.

2nd Feb 2010, 18:36

Hi, I have a 2005 Park Avenue that was manufactured in April of 2004. Do you know if it has a different intake plenium? I asked the dealer and he said that the same part number was used from '97-'05.

4th Feb 2010, 01:17

Basically it's the same manifold. Slight upgrade in 2003. The main change was in the EGR bore passage width. Slightly smaller to allow for an air gap.

4th Feb 2010, 18:06

So do I have to worry about the coolant leaks? I had a '99 Park Avenue previously, which I never had this issue with. I have heard that the '99 Park Avenue was recalled for this issue, but don't know for sure as I bought it used.

29th Nov 2010, 14:39

I fixed my 98 LeSabre problem with the upper plenum with an aftermarket plenum that cost 70 bucks at Parts Geek, plus spark plugs, oil and antifreeze, in about 4 hours. It went at 125k miles, and has run to nearly 200k.

Still has original hoses, belt, water pump, timing chain and alternator, which is starting to squeak. I will buy all the leaky Buicks I can cheap. This car still runs great, but has a little lifter noise cold, which is no big deal, and really means nothing.

I haven't even had to change any front end parts, except one right inner tie rod. Big deal. No CV shafts, no nothing, just that problem, which could be avoided to some extent by checking your coolant, and if it goes down without explanation, you should check it out by pressurising your coolant system, and if it doesn't hold pressure, it's leaking. Not rocket science.

These plenums not in all cases start with a small leak, and finish with a big leak, so if you open your hood once a week to check your oil and coolant, you just might save a lot of problems; it's not a big deal, nipped in the bud, and if you have an honest mechanic, 4 or 500 bucks is peanuts to get a car fixed. That doesn't even do a full brake job for that anymore. Gees.

13th Jul 2011, 19:27

I agree. THANKS.

13th Jul 2011, 19:31

I had almost the exact same thing happen with my 1997 LeSabre. Ran fine after the plenum repair. Now have noisy lifters on start up and for maybe 5-10 minutes afterward. Runs rough and hesitates also during the 'noisy' time. Runs great after warm up. ANY IDEAS??


9th Oct 2011, 14:32

I feel bad for you and your son. My 98 LeSabre ruined my savings TWICE, and it is about to happen again... After a while you can sense it is going to fail... Too bad it is too late to NOT bail out GM... They are the worst car company in the US for not owning up to this mistake... I am going to look into suing them.

28th Oct 2011, 17:47

Just because you are dissatisfied with your Buick, doesn't mean you have to sell out the American car companies and buy foreign. Don't be too sure they will help you any more than GM. Besides, our economy now can't handle too much more in the way of imports. Be American, Buy American.