If its a 3.5, the insert piece that surrounds the license plate is where the water is coming in. It then FILLS the spare tire well, when it rains heavy. The dealer fixed for me under warranty back when the car was newer.
To fix sunroof in a 200 Oldsmobile Aurora, first detect where the leak is coming from. Apply marine sealant to the affected area and let dry completely.
Fix the leak, and fill the coolant.
I just read that there was a recall on the fuel lines and other parts sometime in 2004. Google "recalls on a 96 olds aurora" and it will list it.
Probably a vacuum leak. Do you have a code P0171 or P0174?
I have the same problem on my 2001 Olds Intrigue. It appears to be a leak in the trunk deck at the point where the power connects through for the brake light in the spoiler.
You have to take off the belt first. It can get very tricky because if you don't know how to put the belt back on then you have another problem. After you do that its pretty visible what you have to do. Make sure you have plugs so your fluids won't leak
you have a leak or a hole in a air bag or air line
There are multiple locations for which to trace an oil leak. These are the filter mount, cooler hoses, the cooler itself, oil pan and gasket, valve covers and main seal.
A bad trunk seal weatherstrip.
Have you checked the Gasket that goes around the Trunk opening?
I had the same problem with my 1992 Accord. Replacement of the trunk lid gasket fixed the leak, but I had to special order the gasket from a dealer.
My question, I didn't finish. Water intrusion into battery storage compartment in rear seat, which spreads to passenger side floor mats. Where's it coming from?