I have acquired a 1998 Buick LeSabre with a coolant leak at the intake. The known intake leak problem for these cars was supposedly fixed on this car; (car was in the family so I believe this to be true). I am guessing that something that was suppose to have been done was not done. I don't have a shop manual for this car like I did with my old '93 Buick. So what I am asking is what I should do to correct the issue, what might have been overlooked, what I need to obtain, any diagrams that will help me to disassemble. etc.

With the coolant pooling inside of the air intake duct; where does that indicate the leak is occurring? I checked with family and the person that did the work is a knowledgeable mechanic; although we all can make mistakes at times. I don't want to be tearing into the car before I know more about what I should tear into.

I've never seen it come back in the intake duct like that before. Either way, the repair that was made before, isn't/wasn't the correct fix. The problem back then was repaired, but using the same parts that were installed at the factory. Their is a newer style of intake gaskets that prevent this from happening. Based on where the coolant is in the duct, I'm going to assume this is the upper manifold gasket issue vs the lower gasket.

While your at it, check your oil level please.

This car was properly maintained as far as regular oil changes. I checked the oil and don't see any visual indication that coolant is in the oil; I assume that it would be a milky/murky colour.

How do I make sure I get the proper gaskets for the repair?

Hmm, hard to say with this one Kim because we don't know what kind of gaskets was used for the lower ones. The key thing here is we need to worry about the upper manifold.

If you want to be sure 100%, replace the upper plenum completely with new gasket. This will probably cost around $90 depending where you get it from. This should be the newer design that prevents the EGR port from melting and allowing coolant to enter the plenum.

2nd, get the metal framed gaskets for the lower intake manifold. Replace them too while you have the upper off.

If the gaskets are that expensive then it only makes sense to do the lower intake as well as well as the upper.

Correct. It'* always best to replace them both at the same time.

While your at it, you might as well upgrade the plastic coolant elbows to the aluminum kind. These are a high failure part also.

I am with Mike on replacing the whole upper intake, the redesigned ones have strengthened baffles so you supposedly don't risk having the upper intake explode if the fuel pressure regulator diaphragm ever fails.
I don't think any changes were made with it in regards to coolant leakage though, well other than the reduced diameter EGR Stovepipe, that helps keep the EGR Coolant Ports cooler, that way they do not warp around the coolant ports that go into the upper intake manifold/throttle body.
One thing that can happen with the upper intake manifolds is the plastic channel that holds the throttle body gasket in place can warp, but usually that only makes it leak externally.
I cannot think of what would cause the coolant to get into that part of the throttle body though, it would have to be a lot of coolant leaked inside the upper/lower intake manifold for that to happen.

Let me get you some part numbers, if you still need info on the installation I can provide it, I have pics of the bolt tightening sequence posted already somewhere on here, as well as videos from the job being on on a supercharged 3800 II, which the gist of that process is the same as on the naturally aspirated motor.

DORMAN Part # 615180 - Upper Intake Manifold with new gaskets and reduced diameter EGR Stovepipe.
The link above is for one of the cheapest places I have seen the manifold sold at, if you want to be sure you have a more reliable warranty on the part, then get it from RockAuto, you will pay a few bucks more, but they have better warranty policies than Amazon.

FEL-PRO Part # MS98014T - Lower Intake Gasket - Cheapest place for this that I have seen is RockAuto, so you may want to order them both from RockAuto.

DORMAN Part # 47065HP - The Aluminum Cast Coolant Elbows, RockAuto carries them as well, but they are not always in stock, if they are not check a local auto parts store, just be sure they are aluminum.

A tip for the EGR Stovepipe that is on the Lower Intake Manifold, use some channel lock pliers on it for removing it, you may have to tap on them with a hammer a few times, but it should come out, when it does use the old one to tap the new reduced diameter one into place, it will fit over top of it well, and make installing it just right easier.

last couple times i did this rock auto had it all for maybe 120-130, amazon i used to buy from a ton but lately they have been pushing that terribly expensive prime, and waiting on the free shipping a week or two. rock always ships it fast

I spoke with the previous owner of the vehicle. He told me that when they repaired the coolant leak they purchased the new and improved upper intake manifold; although I was not provided with any particular part number; they may have this on an invoice so might could find it later if they still have the paperwork. They also replaced the EGR valve. The lower intake manifold was not pulled and thus the lower intake gasket is the original. He told me that when they discovered that the coolant was "disappearing" that it was so slight over a long period of time they just added new. I guess they figured the intake leak had been repaired and thus of no concern to the problem. I am not driving the car with an intake leak; I drove it Friday without knowing it was the intake but the possibility of filling a cylinder with enough coolant to cause major damage means it sits until fixed.

If they brought the new and improved upper intake manifold and it is OK, can I get by without buying a new one; is it possible it is just a gasket issue. The previous owner did not mention the EGR stovepipe; just EGR.

Can a lower intake manifold leak place coolant inside of the intake duct like is shown on my photo?