Porsche 993s came with two different styles of power steering reservoirs; the early car's reservoirs were transparent with a minimum and maximum mark on the side. You would check the level by viewing the fluid between the marks. These reservoirs were replaced with black reservoirs with a dipstick attached to the cap. The transparent reservoirs are no longer being produced but if you are replacing a transparent reservoir with a new black one, the new reservoir will come with the dipstick/cap included. The level is set with the fluid warm and the engine idling with the vehicle on level ground.
Porsche also changed the type of power steering fluid that they use in the system. Up until March of 1996 Porsche used Dexron II D ATF and for cars produced after March of 1996 Porsche switched to Pentosin (CHF 202) fluid. These fluids can be mixed and you can add Pentosin to Dexron if you are topping up the system but both Porsche and Pelican recommend you flush, refill and bleed the system with Pentosin. Please see our article on flushing and bleeding your power steering system.
If you are replacing your reservoir now is a really good time to check all of the hoses and replace as needed; please see our article on power steering hose replacement for additional instruction.
The power steering reservoir is located inside the engine compartment on the right side. You can probably get the reservoir out and the new one in by just removing the airbox lid but I like to remove the box (red arrow); it gives you a lot more room to work, some of the hose clamps can be difficult to get to and power steering fluid is really slippery and messy and the extra room helps keep the mess to a minimum. Please see our articles on Varioram and non-Varioram airbox removal for further instructions.
With all the fluid you can get sucked out from the top removed place a few rags under the reservoir (yellow arrow); even though you have removed the fluid some will still be in the bottom of the reservoir and spill out. Depending on whether you have an original reservoir or who replaced the one in your vehicle in the past you can find all kinds of differing hose clamps. Use the correct tool for your clamps and remove the supply hose (red arrow)
The reservoir is held to the bay by a clamp that wraps around the mount on the inside (yellow arrow). Depending on how easy it is for you to get at the return hose on the bottom of the reservoir you can either loosen the clamp or remove it as we did to remove the reservoir from the mount. Remove the clamp on the return line (red arrow). Inspect the lines for bulges, drying or cracks and replace as needed. Installation is the reverse of removal.
To bleed the system: Refill the reservoir and quickly turn the motor on and off; this will cause the level in the reservoir to drop rapidly so do not let the engine run long as this can introduce air into the system. If possible have a friend watch but do NOT let the reservoir run dry. Once you can start the engine and the level does not drop let the motor idle and turn the steering wheel quickly and at an even pace from lock to lock several times to bleed the air out of the system. Do not force the wheel when turning. Continue this procedure until the level remains constant and there are no more air bubbles in the system. The level is set with the fluid warm and the engine idling with the vehicle on level ground.