You can find the reservoir on the left side of the engine. Inside a baffle plate is present to avoid fluid spilling when pour. Both compartments have a see through glass in order to check the level of the fluid in the reservoir. The reservoir is divided in two parts in order to keep the dual system independents, both systems have their own filter. The front side feeds the front accumulator while the rear side feeds the rear accumulator and the master cylinder brake system.

Sensors were added to the reservoir on later cars in order to warm the driver if the level of hydraulic fluid were to be low by illuminating two warning lights. The hydraulic fluid to use is Castrol RR363, after chassis number 50001 the fluid is changed to mineral oil. If you see a green label on top of your reservoir or on some of the hydraulic components then your know your classic uses mineral oil. These two oils are never to be mixed, mixing them or pouring the wrong one in the system will cause permanent damage to hydraulic components and you will need to replace most of them as well as all the hoses present.

For all car models before chassis number 42,000 (non mineral oil) here is a diagram with all the parts and a list of the right reservoir for your model depending on your chassis.

For car models after 50,000 chassis number (mineral oil) here is part number UR21449 and for a complete view on the diagram click here.