So, my brother0in-law just bought a 98 Se. Since mine was a 95 I was wondering what he should look out for. Was the DEX cool still an issue in 95? Tranny problems? The UIM thing still a problem? Any new problems for that year. I believe he got a 3 yr warranty, but still want to let him know what to watch out for.
And, I know someone is going to want pics, sorry, haven't even seen it yet.

Since a lot of the gearguys are in Toronto, and willwren has got to be exhausted, let me start this out.

I believe (from a previous post) that Dex-Cool was introduced in the 96 Bonneville and definitely was used well beyond the "98. So that should be flushed out, and either the new replacement stuff introduced this year (or the old green stuff) should be put in. That should be done right away.

The Series 2 engine was introduced in '95, and that'* the one that had the aluminum lower manifold (LIM) and the plastic upper manifold (UIM). Lots of problems with the EGR tube burning the plastic UIM! This is well-documented in the 92-99 forum and in techinfo.

So on the '98 (which I've been through on ours), it needs to be looked at very very carefully for leaks, coolant in the oil, white exhaust, significant loss of coolant level, etc. Many of the gearguys will not argue that replacing the UIM itself and putting in the new GM aluminum framed LIM gasket is a good preventative maintenence item. I agree!

We have not had tranny problems on our regular old Bonnevilles, but then they are my wife'* Bonnies, and she is a "non-spirited" driver.

The real "gearguys" will have more to add.

The 92 - 99 is not my forte, but Slug has covered the main concern pretty well. I assume as long as you've been around, you're familiar with the techinfo article on the intake problems. The '98 didn't really introduce any "new" problems. There may be problems with the air mix actuators, or vacuum hoses - but nothing much different than from your '95. Have him check the transmission and other fluids, plugs, wires...the usual stuff.

Thanks for the start. I will tell him to get that dexcool out right away. As far as the UIM i know he'll be stubborn and wait for ti go go and let the warranty cover it, but I'll warn him.

The Dex-Cool color is "hot-pink", that'* the tip-off. It'* possible it'* already been replaced, but a good flush never hurts. The replacement coolants are offered by Prestone and Peak. The Peak is amber colored and says it can be mixed with any coolant. So if every drop of Dex-Cool is not removed, there won't be any reactions.

Stay on your brother-in-law about the UIM/LIM issue. The '98 Bonnie is a great car and it would be a shame to lose it'* great engine! But it can happen. (we can always arrange to get willwren on his case )

Just have him wait a week or three and bring it in; tell them he had problems out of town and diagnosed it to a leaking UIM & LIM. I've no doubt they find both. I've got no faith in the factoru setup running this long without problems. Check the production code on the uim first, it may have been done already.

Yeah I'll check it out as soon as I see it.
Besides, I'll have to teach him how to drive it.