Well my buddy who is a Buick tech for the last 20+ years just called to let me know the car is all ready. He did the lower intake gaskets, upper gaskets and valve cover gaskets, along with a new set of front pads and rotors. Took him 3.5hrs and I payed him $150.

He did not use the Ken-Co kit on my car because it already had the revised lower manifold with the smaller EGR tube in it. I don't know if the manifold is original or if it was replaced before I bought the car. If it was original that means that GM made the lower manifold change sometime in 99. My upper manifold was obviously fine plus it was a Delphi unit as well.

So now I guess I need to sell my Ken-Co kit to someone on this site.

Some here have said the manifold change came through in '99. My car was manufactured in July of '99 (must have been right before shutdown for retooling the model change) and has had 105K trouble-free miles, with the exception of changing a throttle body gasket.

Others here haven't been so lucky. Damned shame they don't sell the small O.D. EGR transport tube as a separate item.

So could I just order a new lower for my car to fix this problem instead of the Ken-Co kit and have it over with? If so can I get a part number...a part number on the upper would be nice too.

As I understand it, GM'* "fix" in '99 was to reduce the diameter of the EGR pipe from 3/4" to 5/8", thus providing an air gap between the hot pipe and the plastic upper manifold. (The bore of the manifold remains at 3/4".) If that really does fix the problem then all you need to do is install a reduced diameter pipe in your lower intake and you have the same thing as a '99 LIM. Maybe they changed something else on the manifold, but if so, I have yet to hear about it.

It might be a good idea to find out how many failures of 99+ manifolds there have been. I was talking to my buddy Dan, an ASE mechanic who worked for a Pontiac dealer and now works in an independent garage. He says that he has changed 99+ uppers that failed by burn-through same as the older ones. I don't know if it is less likely, or if you get more miles than the '95-98, but they DO fail.

I still think the best insurance is to use a 5/8" pipe AND a 7/8" sleeve- or the KenCo kit.

Bill,

Did he say if any or all of the 99+ models that failed had the reduced diameter stove pipe? It would be interesting to know. I think the TSB that GM issed recommending replacing the lower and upper manifold for coolant consumption problems was dated July of '01. Makes me wonder when they put the new lower manifold on the production line. I think the sleeve in the upper is a great idea. I have a question in my own mind on how the heat transfer from the metal to the surrounding plastic is going to affect things, if at all. I am convinced that it can't make it any worse.

You probably don't want to hear this, but.......The heat damage on the upper is not very obvious unless you do a little careful scraping in the hole where the EGR pipe runs. If your mechanic did not carefully check this for you, you might have the kind of hidden damage that destroys engines. You might want to consider installing the sleeve from your KenCo kit in that upper as insurance. We have yet to hear of a sleeved upper failing. Since the gaskets are practically new, you probably would not have to replace them. Not that much work, and you already have the parts. Just a thought.

Dan said the uppers fail with the smaller pipe, too. I don't know if they run longer, or fail less frequently than the older design, but I know they DO fail. The sleeve works by reflecting the heat from the plastic, as a heat shield. Conduction of heat to the plastic would be a problem, but is minimized by the air gap when you run a reduced diameter pipe. In addition, if the sleeve sticks up just a bit into the air stream, the incoming air will help to keep the sleeve and the plastic underneath it cool. I am evaluating the height of 7/8" OD sleeve needed to protrude just a bit into the air, allowing the pipe in the center to get most of the cooling, as GM did. GM bet that the air gap alone would be enough to solve the problem, but it apparently was not. :( That'* why people buy the KenCo kit. The only issues I have with the KenCo kit are the price and the really big change in EGR flow rate and velocity induced by a pipe that allows for half the flow of the new GM design.

Thanks Bill. That answered my questions. I guess I'm going to find out how long things last with the smaller stovepipe and no sleeve in the upper. If it fails again this car may be cut into little pieces and sold for scrap.

Could it be that GM changed the dia of the nipple sometime during the 99 model year
so you have some with the old design and some with the new out there?

I think that is possible, even likely. I wish someone who has seen a newer LIM would chime in here. I have been curious if GM'* solution was to change the seat for the EGR pipe in the LIM from 3/4" to 5/8". That would have allowed them to use a cheaper, straight piece of 5/8" stainless tubing as a pipe instead of having to fabricate a reduced diameter pipe with a 5/8" body and a 3/4" base as we are doing for the older L36'*.

[edit: It would also make the new GM pipe incompatible with the older manifolds.]