I just pulled my upper intake manifold because the coolant consumption was getting bad enough that the car shouldn't be driven. The car has 73k miles on it now and the dealer had replaced the upper manifold at roughly 36k miles. It is a Delphi unit with a mfg. date of 7/11/00. The lower manifold was soaking in pools of antifreeze. There were two distinct problems. The first issue was the upper manifold bolts were not much more than finger tight. I realize that a lot of time and miles have passed since it was replaced but I would not have expected them all to be as loose as they were. I would highly recommend some thread lock for these bolts. The second issue is the opening for the EGR tube looked pretty good until I scraped on it. It is so soft that a hole immediately opened into the coolant passage. It was only a matter of time until it failed completely. It'* a good thing I didn't just torque the bolts and keep going. I have a new Dorman upper and am waiting for gmpartsdirect to deliver the new lower. I won't pull the lower until I have the replacement in hand. It will be interesting to see what the old gaskets look like.

Based on what I have seen on this vehicle and read in these forums, I'll say that replacing an upper intake manifold without reducing the EGR tube diameter is risky and a temporary fix at best. And even at that only time and miles will tell us how good of a fix reducing the pipe diameter really is. Shame on General Motors. They produced a great engine but saved a couple of bucks in the wrong place.

My opinion, worth price charged.

You kinda' have to do this to believe it. Looks good, but turns into a material like charcoal. Yeah - shame on GM.

Bill I think it may have been one of your previous posts that convinced me to scrape on the plastic to see if it was good. It looked fine. If a person just went with a visual inspection and didn't probe it a little they could very easily put a failing manifold back in service. In any case I'm grateful for all the good information on this forum. I've poked around on other automotive forums and have yet to find one as informative as this one. My hat is off to all involved.

You'll be very surprised at the condition of your lowers. Mine were trashed at only 77K miles. The UIM, however, looked excellent.

I agree with what you said about the upper bolts becoming loose. My upper was leaking coolant onto the lower manifold. So, I popped off the fuel rail and checked the torque on those bolts. All 11 were only at 35 - 60 in. lbs. So, I retorqued them to 89 in. lbs. in the proper sequence, using the Permatex blue thread locker. Nonethless, I still have the leak. So, looks like I'll be doing another UIM on it. This time I think I'll have it done (time is too precious right now) and I'll use a Dorman. Lowers should be fine, however.

If you replace the upper, as it looks like you'll have to, could I have the trashed one? I'll pay postage. I just ordered a set of reamers to ream out the trashed plastic and have some 7/8" stainless steel tubing for a sleeve to be epoxied into place.

If you're game, PM me. I have one done, but I'd like to do a few more to see how this works.

Vital the worst part of pulling my manifold was the throttle body bolt behind the support bracket. I was able to get a wrench on it by removing the thermostat housing. I could turn it a tad at a time until I could get it off but it was a pain in the back. I suppose there is a better way but it was not obvious to me. I'll let you all know what the lower gaskets look like when I get it apart. And when it all goes back together Loctite will be my new best friend.

Bob - The manifold is all yours if you want it. I'll see if I can figure out this PM deal. I have the box that the Dorman came in so I can ship it in that. It may be a week or so as I set the Delphi back on to cover the lower until my new one arrives from gmpartsdirect.

RG: Got the PM; you have a reply. I have one upper sleeved, and if you're willing to be the test mule, we can just swap manifolds.

Bob you have a message.

This thread makes me want to take mine back apart and install the reduced dia tube.
Or I guess I could wait until she starts using a little coolant.
Wasn't someone making up reduced tubes? Don't have time to machine one.