99 has a cracked lower intake manifold

[sleguy]

That's actually what I think I'm going to do. I'm going to order the "Sure Fix" UIM kit from ineedparts.com, the aluminum LIM gasket and elbow from a GM dealer, and probably a used LIM just for the heck of it. Its probably a good time to do spark plugs and wires too. I'm still unsure if I'm going to do it or not, but I figure either way, I want to make sure that these specific parts go in rather than whatever a particular shop might order.

I don't think the crack is a casting line, simply because its not straight. But I'm beginning to suspect it really isn't the source of the leak either... at least not externally. There just isn't a whole lot of gunk around the crack. Its closer to the LIM gasket. Also, the coolant passages seem to be closer to the center, not the ends.

As for the elbow, after looking at the picture (rather than the car), you can clearly see some coolant leaking from the right side of that elbow. I didn't see that looking at the actual car.

The oil was just changed a week ago, so it looks fine right now. The bottom of the oil filler cap doesn't have any white stuff on it, but it does have some bubbled condensation looking drops.

Since the UIM was done by the GM dealer before I took delivery, its probably a GM part. The date code is from 2003, though. Its been running Dexcool its whole life.

Don't you think with the mileage since the last tear down that it would be good to do the whole top end. UIM, LIM, plastic elbows, Prestone "mixes with any" antifreeze.

[willwren]

I replaced an IMPROVED DESIGN GM unit in my driveway 2 years ago that was about a day from total failure. Original and improved GM designs are JUNK. If you didn't install a sleeved UIM, it'll be at risk anywhere from 3-10 years later. The one I replaced was probably only 3-5 years old (estimated, as the work was done by a previous owner).

[94SilverSSEi]

Actually that was what my old one had it was about 3-4 years old with 90-100k.

Even with yellow coolant do they still wear out that fast?

[00Beast]

Yes. These aren't as much affected by Dex as they are by the EGR.

[olblueeyesbonne]

I replaced an IMPROVED DESIGN GM unit in my driveway 2 years ago that was about a day from total failure. Original and improved GM designs are JUNK. If you didn't install a sleeved UIM, it'll be at risk anywhere from 3-10 years later. The one I replaced was probably only 3-5 years old (estimated, as the work was done by a previous owner).

DITTO!! I have seen SOOO many GM replacement UIM/Plenums failed or close to it with less than 3 years of use. I had one come through last summer that was 7 months old and was already a goner. I had the customer take it back and get their money back on it as I replaced it with a Dorman for 1/4 the price they were charged, including labor.

sleguy -I have a couple LIM's here and could send a nicely cleaned unit that's ready to install for $40 to IL. I could send it out tomorrow and you would have it Tuesday with Spee Dee Deliveries 1 day service from Minnesota.

[sleguy]

sleguy -I have a couple LIM's here and could send a nicely cleaned unit that's ready to install for $40 to IL. I could send it out tomorrow and you would have it Tuesday with Spee Dee Deliveries 1 day service from Minnesota.

That sounds like an offer too good to pass up. Sure, I'll PM you.

[Bing]

Let us know what you find with the LIM when you pull it off. Glad to hear your able and willing to take a try at this. It'll definitely save you money and your confidence toward doing more work on the car will be boosted.

[sleguy]

I think I was the victim of an elaborate optical illusion. I got another LIM from olblueeyesbonne today. To my surprise, the location of my "crack" is indeed a casting line on the other LIM. The casting line was much more pronounced than I expected. By that I mean it sticks out a lot further than I thought. What I thought was a crack seems to just be dirt and gunk that built up along one side of the casting line. So the LIM itself is probably fine.

I'm still going to do the gaskets and the UIM, but I've decided to just take it to a local shop. I'd like to do it myself, but I don't have all the tools I would need and it would be hard for me to make the time. Our 02 Buick Rendezvous is turning into a POS with problem after problem. So I have to clean it up and start car shopping this weekend. This just seems like the quickest path to having at least one reliable vehicle again.

It just goes to show you; if you go looking for problems, you're bound to find something, whether its really there or not. So the Bonneville is going to go to the shop Tuesday. I'm going to ask them to save the old parts for me to look at. I'm curious to see what they look like after almost 100k miles.

[willwren]

Use the aluminum-framed LIM gaskets and the Dorman or APN UIM now. Do NOT wait. And get the DEX out of there!

[sleguy]

Yep. I've got the aluminum LIM gaskets, the APN UIM, and a new coolant bypass elbow sitting in my basement ready to go. Tuesday is the day.

Use the aluminum-framed LIM gaskets and the Dorman or APN UIM now. Do NOT wait. And get the DEX out of there!

[sleguy]

I had the work done by a local shop today and got my car back this evening. I didn't get a mile before the Check Engine light came on. I was picking up the car after hours, so I drove it home and pulled the codes. P0108 and P1106, both related to the MAP sensor. The sensor appears to be firmly seated and the electrical connection looks fine, so I'm not sure what the problem is. Is there something they could have screwed up or is this just a major coincidence that the sensor went bad just now?

Full disclosure, in 2003 after I had just gotten the car, my dad was looking at stuff under the hood. He removed the MAP sensor and when he went to put it back in he broke off one of the side clips. I taped it down with electrical tape and its worked fine that way for the last 8 years.


As far as the old parts go, the upper intake plenum and gasket looked perfect. They probably could have been reused. The lower intake manifold itself was fine. There were no cracks. It was indeed a casting line I was looking at. My coolant leak was most likely caused by the lower intake manifold gasket. Its the old plastic model and it definitely has some deformation to it. I'll take some pictures and post them soon.

[olblueeyesbonne]

I had the work done by a local shop today and got my car back this evening. I didn't get a mile before the Check Engine light came on. I was picking up the car after hours, so I drove it home and pulled the codes. P0108 and P1106, both related to the MAP sensor. The sensor appears to be firmly seated and the electrical connection looks fine, so I'm not sure what the problem is. Is there something they could have screwed up or is this just a major coincidence that the sensor went bad just now?

I'm betting they broke the MAP sensor when they tried removing it -I've had soo many break open on L36's I've snatched up a mess of them.
I will try and get one packaged up and shipped out tomorrow -pm me tomorrow night to verify I did -I believe I still have your address here, but it might not hurt to pm it to me for good measure.

[sleguy]

Here's the pictures:



UIM looks good.



No melting around the EGR hole.



The other end looks okay too.



Here's the real problem on the LIM gasket.

[olblueeyesbonne]

LIM gaskets were definitely gone, oh, several years ago.
Plenum gasket is showing deforming around the coolant ports near the EGR hole.
It's hard to see from the pics (on my computer screen) the condition of the EGR hole from the Plenum gasket to the Plenum inlet -if there is any corroding or 'fraying' that's a sign of plenum failure.
Also, can you tell me at what numbers the arrows are pointing at on the time dials on top of the plenum? Does it say "GM" near the top TB stud?

[00Beast]

Take a metal nail, pick or something like that and poke the plastic in the EGR hole, the sides. Does it deform or is it still firm? Sometimes it can look fine and be just on the bitter edge of failure.

[sleguy]

It was, in fact, a GM UIM with date code 1/28/2003. I poked at the plastic around the EGR hole a bit with a drywall screw and it didn't seem brittle. But I do now see that one of the holes near the EGR hole is not perfectly round. All in all, it seems like it was in good shape for the age and mileage.

I think I must have lucked out with regard to the LIM gasket. There must have been enough sludge that built up in all the right places to keep my leak small.

[Billha]

If you don't mind my asking, how much did they charge you for labor? I might opt to pay someone to replace the LIM gasket on my '02 Park Ave Ultra when the time comes.
Thanks.

[sleguy]

The only "parts" I didn't supply were oil, coolant, and an oil filter. They basically did 2 oil changes after the job to flush things out. So the labor was $425 and the parts (that I didn't supply) were $58.

[sleguy]

I got the new MAP sensor in this evening. Thanks to olblueeyesbonne for the sensor. Since the old one came out in two pieces, I think I can rather definitively say that I found the problem. The scan tool is getting good readings off the new sensor, so its all good now.

With the Bonneville all fixed up and the new Grand Prix, we're finally back to 2 reliable vehicles again. I'm happy.

[willwren]

Well done, very well done.