Ok guys first off, I had her in 2yrs ago for hydro-lock and the dealer replaced the upper intake and gaskets. $800. 40,000mi later, I noticed a slow loss of coolant and the other night I lost heat and the engine temp rose (not to the red). I added around a gallon of coolant and it was gone in 3 days this time. During the 3 days, I found some milking of the oil under the fill cap and it'* been running rough and blowing some vapor out the exhaust. I am guessing it'* a gasket or plenum failure again, so I made an appointment at a local Pont dealer who quoted me much lower this time to do the job. Now if they decide the plenum is bad, I have the option of the $300 GM part or $140 for the Dorman Intake Kit with gaskets. Gathering info on this site, I hear the GM part or gasket has been improved but I asked several dealers and they thought only the gaskets have been changed. Any Idea if the Dorman is better? Thanks for any suggestions

Both the GM and the Dorman are improved. A couple members have gone to the Dorman already, but nobody has put enough miles on it to know. Their cars are running fine currently.

Here'* some advice for you:

There is a couple of "alternative" choices now available to the Series II 3800 NA owner though.

Here'* the CHEAPEST!
http://www.bonnevilleattitude.com/st...3aea7add156b15

Next choice is the aftermarket Intake Manifold replacement.
http://www.bonnevilleclub.com/forum/...pic.php?t=8522

Finally there is the GM Dealer solution.
Posted in TSB below.....

Engine Coolant Consumption or Coolant Leak
(Inspect for Material Degradation/Replace Intake Manifolds) #01-06-01-007A

Models:
1995-1997 Buick Rivera
1995-1998 Buick LeSabre, Park avenue
1996-1998 Buick Regal
1998 Chevrolet Lumina, Monte Carlo
1995-1996 Oldsmobile Ninety-Eight
1995-1998 Oldsmobile Eighty-Eight
1998 Oldsmobile Intrigue
1995-1998 Pontiac Bonneville
1997-1998 Pontiac Grand Prix
All With 3.8L Engine (VIN “K” – RPO L36)

Comment:
Some owners may comment on excessive engine coolant consumption, or an engine coolant leak near or under the throttle body area of the upper intake manifold.

Cause:
Upper intake manifold composite material may degrade around the EGR stove pipe and could result in an internal or external coolant leak.

Correction:
1. Follow the upper intake removal instructions found in the Engine Unit Repair Section of the Service Information Manual.
2. Inspect the inner diameter of the EGR passage for signs of material degradation. Degradation will appear as “pitting” of the composite material in the EGR port passage.
3. If degradation of the upper intake manifold composite material is found, replace the lower and upper intake manifolds with the following part numbers:
> Lower Intake – 24508923
> Upper Intake – 17113136 (includes necessary upper intake plenum gaskets)
> Lower Intake Gasket – 12537197
4. Follow the lower and upper intake manifold installation instructions found in the Engine Unit Repair Section of the appropriate Service Manual.
5. If degradation is not apparent, skip to Step 7.
6. Verify the repair.
7. If no degradation is found, evaluate the vehicle for other causes of excessive coolant consumption as noted in the Engine Diagnosis Section of the appropriate Service Manual.

Hi

I went the Dorman route, but with only 6000 miles on it..too soon to tell. Its looks much more substantial in the problem areas, but again..only 6k.

I went with the dorman also. Check out this post for some pics.

Changing Upper Intake w/pics.Updated Finished.Dialup Beware

If you look at the pics of mine I would seriously recommend going all the way down and have the lower gaskets replaced also. I think that is where most my problems came from.

Also look into going to 180 degree thermostat and a transmission cooler. The cooler engine will help the upper intake last longer.

Also check out this post it shows the improvements to the dorman upper intake.
3800 series II, Aftermarket upper intake information...Pics

I believe someone posted that GM uses the aftermarket one for theirs, or they're using the molds. The new GM ones aren't made in the same country as the originals.

Hi

We did the lower gaskets as well. I was glad I dd after seeing the degradation.

The two potmetal elbows were replaced as well.

In an effort to clear up the confusion...

Are the upper intakes on the 99 Series II defective also? I have been reading all the horror stories about them going out on the Series II, but none of them have been on the 99 model. My car has about 75K and I am showing no signs of leakage.

Also, I noticed in this same thread on DeathRat'* post that the GM TSB only references the 95-98 Bonneville (and only up to 98 for all other Series II for that matter).

Please advise!

That assumption is CORRECT! I've yet to do a 99 Series II in our Dealership for this problem. The ONLY Coolant Leak Campaign in existance right now is this one:
Customer Satisfaction Program -- Engine Coolant Leak #03034 - (07/07/2003)
03034 - Engine Coolant Leak
All 2000-2002 and Certain 2003 Chevrolet Impala, Monte Carlo; Pontiac Grand Prix, Bonneville; and Buick Regal, LeSabre, Park Avenue

Equipped with 3.8L V6 Engine (RPO L36 - VIN Code K)

THIS RECALL IS IN EFFECT UNTIL JULY 31, 2005.

This one envolves the TB nuts replacement to avoid a coolant leak at the TB base gasket.

Thanks for the follow-up Rat!! That'* a nice relief lifted off my shoulders!!

Not to doubt Rat, but can anyone else second that they haven't seen the 99s with the upper intake failing?? (I just want to make sure I didn't miss it in a post somewhere)...

I'm taking the car to Florida in March....that will be the true test to see if it can survive the 3,500 mile trip round trip in one week!!! Before I go, I'm going to swap out the thermostat for a 180 degree and change the radiator cap.