In your engine compartment , on the drivers side , by the firewall ( the metal wall
that divides the passenger compartment from the engine compartment )
If it looks like a smaller version of the brake cylinder container it is the hydraulic clutch reservoir ( assuming you have a manual ) and you will fill it with brake fluid.
Master cylinder - located at drivers side firewall
DOT 3 brake fluid
Either your parking brake / emergency brake is on or the BRAKE FLUID LEVEL is LOW , in the brake master cylinder located in your engine compartment
DOT 3 brake fluid
brake fluid container right side behind battery.
For a 1997 Mercury Sable : ( DOT 3 brake fluid meeting Ford specification ESA-M6C25-A )
Just normal DOT3 brake fluid.
The brake fluid reservoir in a 1991 Jeep Cherokee is located on the master cylinder. To add fluid, unscrew the cap and fill to the appropriate level with the appropriate brake fluid, more than likely dot 3.
The brake fluid for the entire system is added in the master cylinder container. The slave cylinder does not have its own reservoir.
On a 2001 Mercury Sable : The automatic transaxle ( transmission ) fluid level dipstick is near the firewall , in the area of the brake fluid reservoir , in the engine compartment
A 1993 Mercury Cougar takes ( DOT 3 brake fliud )