I've been doing a lot of research around here about failed upper intakes. My 1997 SE has 126,000 on it. I don't lose coolant at all and my engine runs very well. My family bought the car in 2000 with 47,000 on it and I've had it myself for about 2 years. I've strongly considered doing the dorman intake along with lower intake gaskets and coolant bypass elbow as a precaution. Well tonight I finally took off the engine cover to have a look at the intake manifold. To my surprise the date stamp read 2/16/02 and had the expected Delphi sticker. To me and my mom'* knowledge we don't remember ever having replaced the upper intake and it seems odd that a car we bought in 2000 has an '02 stamp. I'm 99% sure it'* 2002 because the years labeled went around "00 01 02 03" and it for sure wasn't 00 which is the only one that would make sense. I'll talk to my dad later tonight when he gets home to see for sure. Even so, it is the Delphi intake, granted it'* newer. Would you guys still think about looking into an upgrade replacement? I'm definitely willing to spend the money to keep the Bonnie in good order.

Delphi and Dorman intakes are only BETTER, not the solution. I firmly believe the Dillon intake soves the problem.

Here'* the update. I just got off the phone with my dad. Apparently back in march 2002 we had the upper intake manifold, lower intake manifold and corresponding gaskets replaced. The car had 70,000 miles at that point. At 126,000 I'm getting more anxious to take action. I need the car as it'* my daily driver so sending the manifold to get an upgrade by Dillon might not work that great for me. is that what you think is best still?

He has intakes already. You don't need to send yours until after you pull it.

Dillon is tops, IMO.

So you're one of the people that got burned by a dealer into replacing the lower intake also? That sucks. Unnecessary expense, unrelated to the problem.

Yeah my dad was reading the bill to me over the phone... $280 Upper Intake Manifold, $240 Lower..... OUCH! Luckily I wasn't responsible for the car then but since I am now I want to cover my A$$ if I can help it! She'* in otherwise great shape and I want to keep it that way. Gotta love the bonnie!

I'll look more into Dillon'* manifolds to get the details for sure. Either way I'm going to upgrade when I'm home for spring break in March. We have a neighbor that is a pro mechanic by day and works on other people'* cars at night. Honest guy who does great work at a VERY fair price. My family has been going to him for several years now.

It seems like a game of time and mileage.

The 00+ guys are starting to see failures on their intakes. Bob'* sleeved models are very good and have already given members a low cost solution. In 4+ years someone will pull one off and see if the problem is occurring in one of those. Because of how he approached it...I think he'* got the problem solved...

I run a Bob Dillon UIM. Been good for almost 20,000 miles now.

However, PLEASE don't overlook the importance of changing those lower intake gaskets. It is my FIRM belief that if I was to have a failure, it would have been as a result of the lower intake gaskets.

My suspicion is that the dealer replaced your lower intake manifold with the newer design lower that uses a reduced diameter (5/8" ) stovepipe. That is the manifold that GM started using in (late?) '99 in an attempt to keep heat away from the plastic upper. If your dealer did that, they could at least justify changing it out. Mind you, that is charging you $240 for a reduced diameter pipe you can buy with a sleeve for $80 from Ken-Co, have a machinist make for about $50, or make yourself for less.

If you buy a new Dorman replacement plastic upper intake manifold, you will notice that an aluminum reduced diameter stovepipe is provided that will fit into the newer lower manifolds. It has a base that measures slightly less than 5/8" and a pipe a little larger than 1/2". If you use that pipe with a new Dorman upper, you will have an air gap of about .120" That'* almost twice the .064" gap GM provided with the 5/8" pipe in the '99+ models. It is also about the same gap you get when you install a Ken-Co kit that also gives you a sleeve to provide additional protection for the plastic upper. That new Dorman pipe is great for people with the newer LIMs, but doesn't help folks with LIMs produced between '95 and '99 with the 3/4" bore. (I am working on a cheap press-fit 3/4" OD shoulder for these now.)

We don't yet know how well this .120" gap will work with an unsleeved new Dorman upper, but we do know the .064" gap that GM provided is not sufficient to keep the heat from eventually destroying the plastic in the upper. The plastic will last longer, but heat-related failures still occur in the 99+ plastic uppers. That is why folks install a metal sleeve in the EGR passage in the plastic upper. When I do them, I follow the original Ken-Co scheme and use a reduced diameter pipe to provide a decent air gap, and a sleeve to reflect and dissipate any heat that impinges on the plastic EGR bore.

You will be able to quickly tell if you got a newer manifold by examining the stovepipe and the borehole in the LIM where it sits. 5/8" = new 3/4" = old. If you already have the 5/8" pipe, and you use a Dillon sleeved manifold you will have an air gap of about .075" and a sleeve to protect the upper. You should not have to worry about failure around the EGR bore ever again.

Even if you have the newer LIM, you will want to pull it off to change out the gaskets against the cylinder heads. Newer gasket designs are now available that should provide longer service.

I did my uppers and lowers at around 70k as preventative maint.
The lowers were toast but the uppers were OK.
If they changed the intake with the smaller 5/8 EGR pipe it should go farther than the original. But the lower gaskets are allways suspect unless you can verify through the paperwork the actual part number installed.

Is it possible that a third explanation for changing the lower intake manifold exists?
In my particular case, I had some etching/pitting on the lower intake manifold gasket
surfaces which mate to the heads. The corresponding gasket surfaces on the heads are just fine,
but then, the heads are made out of cast iron rather than aluminum.

Attached is a link to my dilemma along with a picture of the pitting on my LIM.
http://www.bonnevilleclub.com/forum/...ic.php?t=48779



As suggested by some of the folks here on this forum, I have used J-B weld to
smooth-up these gasket mating surfaces on the LIM. However, if I was a mechanic at a
Pontiac garage, I don’t think I’d be doing that for a customer’* car. I would think from the Pontiac mechanic’* perspective,
if the condition of the lower intake manifold gasket
surfaces could jeopardize the long term successful sealing of the head gaskets, then
replacement of the Lower Intake Manifold would be required.

After looking at these etched aluminum gasket surfaces, it’* given me a better
appreciation for the value of flushing and changing the cooling systems more often.

Jack