Just keep an eye on your coolant reservoir. If you have to keep adding coolant then look for seepage around the lower intake manifold. I had coolant puddling up on my lower manifold but thankfully no milkshake under the oil cap. I changed the upper manifold with gasket and it solved the leaking coolant. I probably could have just replaced the gasket but either way the UIM has to come off. My Olds88 had about 85 k miles when I changed the UIM.

I agree on skipping the Transgo kit. If you are looking for durability under lots of hard driving then it'* worth it. As an addition to a 20+-year-old low-miles transaxle that won't ever be driven hard it is of no benefit, and might firm things up so much you'll regret it.

No worries. I had a very good mechanic walk through the process with me and that helps a lot. It is a job I don't particularly care to d, maybe I've just done too many of them. LOL. It is a pricey thing to do when it comes to labor, fairly small on the parts cost. Once done though, the 3.8L is arguably the best GM ever made and if you look, there are used ones out there with 300K, 400K miles on them. Should give you many years of trouble free driving.

I agree with this. For the benefit of others, this failure can exit outside the block presenting itself as a leak (as described above). It can also leak internally in the combustion path. Lastly, it can do both.
If the leak goes through the combustion path, it will destroy both your O2 sensors and your Cat Converter, very quickly.

This particular failure will have exhaust gases mixed with the coolant. You will see a darkness to the coolant and a dark ring will form inside the overflow coolant tank. I have had little luck in cleaning the plastic tank as it seems to stain the opaque white color. I usually just replace it as I like a spotless engine bay. I can't help myself.

If you don't have time to get to the repair quickly, I have found using K-Seal is the best product on the market to keep coolant where it is supposed to be. It also works extremely well for head gasket failure. Some people have used this as a permanent fix. If you are having to refill that tank or see that dark ring forming, using K-Seal may buy you time to get repairs done before it takes out those expensive sensors and the converter.

Hi All,
The 88 is out of the shop and back in my hands. Took a while to get to as I had other automotive priorities. It'* running and driving flawlessly. And thanks to you all, I know how to keep it that way.

You've all been most generous with your time and knowledge. Thanks again.

See you around the forums.
John

Great news!

Enjoy!