I believe that is called the power brake booster
On the firewall in front of the driver right behind the master cylinder, it's a round black flat cylinder about a foot in diameter.
drivers side firewall high up and behind the brake master cylinder, it is a small white reservoir with a black cap.
He needed a master cylinder.
If I read you right that would be the clutch master cylinder.Are you talking about the black hose going from the reservoir to the cylinder? Need a more detailed description than black thing.
The master cylinder is mounted inside the engine compartment on the drivers side of the firewall. Look at the upper right hand side of the attached picture (in the related links section), at the two round black caps behind the battery. The bottle on the left is the reservoir for the brake fluid. Underneath that bottle is the master cylinder. Your car may not have the bottle on the right, because that one stores fluid used for a manual transmission's hydraulic clutch.
It is located on the firewall between the brake master cylinder and the wheel well. It should be have a round black cap on top. It is about three by an inch and ahalf. Do not confuse this with the brake master cylinder.
Jacob Black needed a new clutch to finish working on his car.
It is mounted on the front side of the transmission, It will have a black plastic line coming from it and going up to the clutch master cylinder.
It is bolted right on the side of the master cylinder. Thin black squire box.
Its called a chain fire.
On my 1998 renault master 350 its easy. the reservor is under the bonnet next to master cylinder quite small and black . Easy to miss Best of luck Brian
It is located on the drivers side firewall, bolted to the brake booster(large black circular object).