Those may be the intake gasket seals, I used to own a 1996 Sable wagon and currently have a 2002 Taurus with the DOHC 3.0 liter, they use a silicone gasket to seal the upper intake manifold. It must be removed to replace the spark plugs on the rear bank, as you know if it's the same engine, however I don't recall opening the cooling system doing that job, maybe someone got a little crazy changing a thermostat or water pump