Not sure what you're talking about.. :?

There are two machined holes in the lower aluminum intake manifold for the coolant that goes up through the plastic intake to the Throttle Body. These holes are on ether side of the EGR pipe sticking up on the throttle body end of the manifold. If you take the plastic manifold off and tap and plug these two holes there will no longer be any coolant to leak. Once these holes are plugged the only leak you can have with the plastic intake is a vacuum leak.
If your car is idling fine now you can do this and reuse the upper gasket and upper manifold.

Ron: Would that include coolant leaks at the throttle body? I have a '99 SLE I bought new, and now has 104K miles on it. The car has been reliable as an anvil, but it has a small leak around the throttle body when the engine is warm.

I find myself adding coolant about every 6-700 miles now and it'* beginning to bug. Since I have to do the job anyway, would it be worth it to pull the top manifold off and do as you suggest, or is perhaps just replacing the thoittle body gasket a better idea?

No choclate milk in the crankcase, by the way.

By the way, I'm a newbie here and this is a great forum! This is the first Pontiac I've owned later than a 1972 model and despite being a car guy of some 40 years, there'* stuff under that hood that I don't recognize! :?

is coolant leaking down the TB and then on to the trans? if so they your TB gasket is bad, and it is an easy fix

1993 SLE: Yes, it is, but after reading all the horror stories here, maybe it'* time to fix the upper intake problem all at once before I hydrolock the engine?

I sure like Ron'* idea of dry-decking the upper manifold if that'* the case. :?

yes you have a 99 right, most , and i say most, not all problems were fixed in 99. but if you want to relapce the UIM, they you should do the LIM gaskets as well

I've already done all that. It'* not the lower gaskets. I did them at 77K....along with a new upper intake. The upper intake is clearly leaking and not the throttle body. Directly under the throttle body is bone dry. I can actually see the upper intake leaking at the corner down onto the lower intake.

I'm going to buy a Dorman upper along with a new upper gasket set.

Hey Don... Can you circle on my pic where you're specifically talking of? I may very well have a flaw, but not know it. What should it look like? :?

"....almost dead center between the two... Is that a casting flaw in the lower intake manifold or a crack? "

Looks like a crack to me.