It is under the alternator. You will need a flashlight . The cap and reservoir can be seen behind and under the alternator on the passenger side of the car almost to the firewall. You need a thin arm and a small hand to reach it. If you need to add fluid, buy a long neck flexible funnel. It is not easily reached and probably not checked too often during regular servicing.
At the power steering pump reservoir. The power steering pump or reservoir is located on the left side of the engine between the engine and the firewall
Inside the power steering reservoir
At the front of the engine , towards the drivers side of the engine ( power steering fluid reservoir on a 1998 Mercury Grand Marquis )
eny power steering fluid will work
Into the power steering reservoir.
where to put power steering in a 2007 Pontiac gran prix
It is part of the power steering pump assembly.
I was looking at a picture in the 2003 Mercury Grand Marquis Owner Guide and it shows the power steering fluid reservoir at the front of the engine compartment between the engine coolant reservoir and the engine air filter box
To locate the power steering reservoir, please watch this video in youtube by YMSCanadian: http://www.youtube.com/watch?v=quU4QiXTUx0
With the engine off, remove the power steering reservoir cap, and read the fluid level.
The power steering reservoir is in a tough location on this car. It is located at the passenger side, rear of the motor, next to the firewall. The two heater hoses are almost right on top of the cap. You will need a long, bendable funnel to be able to add fluid if need be to reach the reservoir.
Link with picture of where steering fluid goes: http://www.fixya.com/cars/t1612500-power_steering_fluid