I cleaned up the lower intake manifold and saw no problems. I decided to take a closer look at the plenum as I did not see any holes around the egr pipe opening. Using a small screwdriver I started flaking off crud and bingo, found the hole where the coolant leak was coming from. When the previous owners worked on the leak, they must have not know the true nature of the problem; I even wonder if they reused the old plenum even though they said they replaced it as looking at the date stamped on it I would not think it the improved design; if they did, it did not take long for it to burn through again, only several years.

At least now I am confident that once I use the new Dorman kit that my leak will be fixed. I am thinking of skipping blocking the coolant ports since the real issue is the egr pipe burning a hole in the plenum.

Poor oem quality stuff is the reason everyone has to do it. the Dorman one is much better than the oem in many ways.


I have never heard of the lim being craked. The plastic uim warps and leaks and the oem lim gaskets are plastic and they blow out

To be honest I don't think they replaced the whole plenum, if they got that Dorman UIM Kit, and replaced it, then they'd have put in that reduced diameter EGR stove pipe, as you said I don't think they understood the true nature of the EGR port problem, if they did they'd have either swapped that stove pipe, or plugged the coolant ports to the UIM.

Speaking of plugging the coolant ports; what is the consensus on plugging the ports? Should it be done anyway, or just leave it be?

It'* all a matter of preference really, with the new UIM, and the reduced diameter EGR Stove Pipe installed, I don't see the problem occurring again for the life of the car, but anything is possible.
If you want to be totally sure coolant never leaks through the EGR Port internally like it was, or externally like it can, then plugging them should stop this from ever happening.

Agreed. Plug the coolant ports and you won't have to worry about it.

But as was mentioned, I believe where you live should have some weight in this decision. As mentioned, these cars are likely less susceptible to throttle body icing, but that will only go so far when you are dodging polar bears on your daily commute. Again, I haven't heard of a report of throttle body icing in our application, but I wouldn't want to be the first report either.

Where she lives, I doubt she will have to worry about it. I live in Northern NY and don't have issues. When you have irrefutable evidence that it has happened, feel free to post it.

I have already freely admitted that I have never heard of it actually happening on a 3800. That'* 10 years worth of forum cruising talking, and should speak for a lot. Whenever there is talk of disabling a safety system, someone has to be 'that guy'. The OP can do what she wants. I am saying it would simply increase the chance that it could happen, not that it will.

Taking the lower intake off the car was the smart thing to do. The intake ports on the heads were full of this sticky gooey mess; I guess a combination of oil and oxidized coolant; the ones closest to the EGR stovepipe/leak were the worst. I used carb cleaner and rags to get the most of it out of the ports. It definitely reduced the air flow on a few of the cylinders. Any advice on this?

As for blocking the coolant ports to the TB; the coldest it usually gets here for daytime highs is upper 20s to lower 30s and that is rare; we average around the 40s for winter time highs. Today is fairly warm at 48F.

I looked for the plugs locally and could not find them; all the hardware shops are closed, chased off by Lowes and WallyWorld. I would have to order them. I may just skip this as the reduced stovepipe diameter would probably mean it will not reoccur.

I have all the parts now, so I just need to finish cleaning the gasket surfaces and get it back together.