A 1991 VW Jetta's power steering reservoir is located towards the front of the engine bay. The unit can be seen placed on top of the power steering pump.
It is in the frunk next to the battery on the passenger side
IT IS ATTACHED TO THE PUMP AT THE FRONT OF THE ENGINE
Lift the hoods, find the lid to the power steering reservoir and remove the lid. Attached to the lid is the dipstick to the power steering fluid, read the level and decide if more needs to be added.
Check carefully, it may be power steering fluid from the reservoir just above and to the left. Look for a leaking hose or a cracked reservoir.
In the power steering pump
To drain the power steering fluid on a 1991 Mercury Topaz, locate the drain plug at the bottom of the power steering pump reservoir. Place a drain pan underneath to catch the fluid and then remove the plug to allow the fluid to drain out completely. Be sure to properly dispose of the old fluid according to local regulations.
It would be located over on the right (passenger) side of the car, and it will usually be a semi-white reservoir, with a black cap. The top of the cap should even say "power steering" on it. The only other reservoir that would be on that side of the car, would be the window washer fluid, and it would be a much larger reservoir, white, with a bluish tint because of the fluid color. It would be pretty hard to get these two confused.
It is below the steering pump oil reservoir down by the block, follow the short belt on the bottom of the crank pulley and it will be on the left hand side of the motor when standing in front of the car.
either the hose is split or the resivoir is cracked either the hose is split or the resivoir is cracked
Power steering fluid or Automatic transmission fluid
It does not matter on that year, just make sure that it is POWER STEERING FLUID.