This sounds more like a bad cooling fan than a vacuum problem. Insure your fans are turning and are not slipping.
check pcv hose elbow for vacuum leak.
The 1995 Mercury Sable would have come from the factory with ( 5W-30 ) oil in the engines
He would not have had a barometer. He would have had a glass tube stuck into a bowl of Mercury, with nothing in it. Because once the hole was made the vacuum would be gone and the mercury would fall back down to the bowl.It takes the vacuum in the tube to create a barometer.
vacuum is measured in pressure. To get a vacuum you need a negative pressure. that would be inches of mercury hg
Could be a bad inertia switch.
how much would it cost on a 2004 mercury sable
On a 2000 Mercury Sable : The automatic transaxle ( transmission ) fluid level dipstick would be near the firewall just to the drivers side of the engine ( where the transaxle is bolted to the engine )
Replace your transmission pump or get a new transmission.
According to the 2002 Mercury Sable Owner Guide : ( the 6 disc C.D. changer is either located in the center console , the trunk , or the right side of the cargo area , that would be for the wagon version )
Bank 1 and bank 2 is running lean. I would suspect a vacuum leak. Check for cracked, disconnected or broken vacuum line(s). The fuel filter could also be plugged and restricting the flow of fuel.
Many of these systems rely on a vacuum supply from the engine to operate the doors that change the direction of air. When the vacuum supply is cut off the system defaults to defrost mode. I would suspect you have a disconnected, pinched, cracked or broken vacuum line under the hood from the engine that leads to the firewall.
check all your ground wires