OEM Wing Hydraulics
IF the wing is lower on one side,
OR there is hydraulic fluid on the rams or engine lid gasket,
OR the “Failure Spoiler Control” warning is displayed:
THE FACTORY HYDRAULIC MECHANISM IS FAILING.
“NO MORE HYDRAULICS!”
The hydraulic wing lift system can never be fixed permanently.
Factory Wing Mechanism Background
The water cooled Turbo’s rear wing is not a cosmetic part, it is a functional part. For the first time, the Turbo lineup employed a 2-piece spoiler wing assembly built into the rear deck lid. This is the same system as utilized in the Carrera GT supercar. The upper wing is an inverted airfoil. The same principle that lifts an airplane up is used to push the back end of the Turbo down. Down-force climbs as the car reaches top speed, down-force pressure on the rear axle builds up to 20 Lbf [90 N]. The 996 Turbo’s inverted wing extends 2.4″ [60 mm] for the coupe, once the vehicle reaches 74 MPH [120 km/h]. Due to the cabriolet top creating additional air turbulence at the rear deck lid, the wing was extended higher to 3.2″ [80 mm] in order to create the same down force as the coupe. The wing retracts flush onto the deck lid spoiler when the vehicle slows to 37 MPH [60 km/h]. The 5th generation 996 Turbo has a minimal lift at the front axle with a cAF = 0.02 and very slight rear axle down-force of cAR = -0.01.
For the 6th generation 997 Turbo, the 2-piece spoiler wing extends 1.4″ [35 mm] for the coupe or 2.56″ [65 mm] for the cabriolet. The wing area for the 997 Turbo increased by 23% over the 996 Turbo wing, with a down force of 61 Lbf [273 N] at 194 MPH [310 km/h]. The water-cooled Turbos took rear down force to a whole new level.
Porsche® has patents for an extended wing and the attachment device:
However, the “permanently sealed” hydraulic system to raise and lower the wing was designed and supplied to Porsche® by an outside firm near Nuremberg, Germany starting in 1999. It is likely that Porsche® drafted a specification for the Turbo’s wing extension requirements – then went looking for a nearby firm to build something.
The question is why did Porsche® choose such a complex, yet inherently faulty design – perhaps there was time pressure to get something working adequately enough, in order to launch the 5th generation water cooled Turbo for display in 1999. This was the first time such an electro-hydraulic mechanism was used by Porsche®. The 964, 993, 996 and 997 Carrera retractable wings all utilize electro-mechanical actuation devices. Only the Carrera GT, 996 Turbo and 997 Turbo have the electro-hydraulic mechanism. This troublesome hydro-electric mechanism was eventually replaced with something more reliable. Both Porsche® and the mechanism manufacturer have benefited (aftersales repairs) from the 1000’s of replacement mechanisms replaced due to premature failure.
How Does the Hydraulic Wing System Work?
All too often Turbo owners complain about a broken or malfunctioning wing or leaks under the engine lid from the rams or the motor module. The heart of the system consists of an electro-hydraulic drive module with electric motor and jack screw along with two separate plungers.
Operation: A 12V motor spins a jack screw, which pushes the two plungers via a threaded plastic block. The two plungers force Pentosin power steering fluid through hoses into two spring tensioned hydraulic cylinders (rams) connected to the wing. Only the right side ram has a set of “extended” and “retracted” microswitches. The switches send a signal back to the instrument cluster ECU (computer controller) to turn off the drive module motor. The computer tracks the time it takes for the wing to deploy. If it takes too long – a SPOILER FAILURE warning alarm is displayed at the dash. The SPOILER FAILURE warning is also activated if the right side ram never extends fully or retracts fully. (The left side is not monitored) Upon failure, the only protection to keep the motor from burning up is a thermister overheat fuse within the motor can. Strangely, electrical failure protection is lacking, as one fuse in the panel is for the entire back lid electrical; hydraulic system, light, e-latch, etc.
Why Does the 996 / 997 Turbo Hydraulic Wing System Fail?
There are several root cause failures identified. All are likely now, given the age of these vehicles. The entire mechanism sits directly over the motor. The entire hydraulic system gets very hot when the car is shut down, cooking and accelerating deterioration of all components. Of course part of the system is exposed to the elements with the wing up. We are finding a lot of dirt and moisture inside the ram cylinder cavities.
- Starting with the motorized plunger device, a plastic plunger block is often broken, usually due to wear, age, heat or malfunction of a limit switch and motor over-run:
2. There are several potentially leaky seals and multiple o-rings in the plunger system itself:
3. The motor can overheat and self-destruct due to dirt, heat, wear, age or limit switch failure:
4. Each hydraulic plunger connects to a high tension spring loaded hydraulic ram via high pressure tubing and banjo fittings. The tubing and banjo fittings are notorious for leaking.
5. Ram cylinder seals are very delicate, and can become brittle, crack and loose their pliability due to dirt, age, wear, sunlight, heat and other environmental factors. Allowing moisture and dirt into the inner cylinder area allows the plunger and spring to deteriorate/rust and fail.
6. The outer cylinders can be easily damaged during prior repairs or by some other means. This allows dirt and moisture to enter the inner cavity.
7. The high tension spring within each ram is designed to force the wing to lower, should there be a failure. But in reality – it may not accomplish this as one side may fail – but not the other. It is not simply 1 chance of failure, but 3, as the left ram circuit, the right ram circuit or both will fail.
Whenever the wing is extended, the springs are compressed under great tension. This exacerbates failure and leakage at every joint and seal since the entire hydraulic system (2 rams and the motor plungers) experiences excessive hydraulic pressure. The steel springs often break due to age fatigue or rust corrosion:
8. Each hydraulic ram has a non-rebuildable factory sealed inner cylinder and piston. The inner seals often end up leaking as they become brittle and non compliant with age. As shown below, this inner cylinder was cut apart, new seals installed, aligned, hardware store plumbing fittings installed, then all soldered back together. It is difficult not to bend or damage the soft copper tube – or to keep it round during cutting, heating and soldering. Ultimately the heat from soldering the assembly back together can damage the new elastomeric seals. Often rebuild services don’t bother cutting the plungers to renew the seals. Wonder how long this one with hardware store fittings will last?
9. Unfortunately, each hydraulic ram is actuated by a separate hydraulic circuit. If either circuit fails, the wing is crooked and inoperable. This is indicated by a cocked wing, warped engine lid seal or a wet cap on one of the hydraulic rams.
10. Finally, there are a set of two very tiny microswitches on one of the rams that have very intricate and delicate inner workings that easily malfunction. These delicate little microswitches control operation and direction of the hydraulic motor and spoiler failure warning function. There is no fail safe, over-ride or pop off valve for the hydraulic circuit. The microswitches are the only signal to the ECU for switching off the hydraulic motor. They easily fail, and this in turn causes breakage, over pressurization, leaks or other problems. Oddly, the microswitches are only on ONE ram – begging the question, what prevents motor operation if the other circuit leaks and fails? These delicate little switches coupled with hydraulic fluid loss are a major reason for the dreaded SPOILER FAILURE warning.
Two Causes that Accelerate OEM System Failure:
a) Heat: The hydraulic system sits directly above the engine in the hottest part of the car, which promotes accelerated aging and breakdown of all components. We are hearing that cars in hotter climates, once having failed, continue to fail regularly because of excessive heat. Test labs use the Arrhenius method for testing materials or systems to failure under high heat. Why? Because mechanical and electrical devices fail faster at higher temperatures! In effect, our 996 and 997 Turbos are conducting a high temperature experiment on the hydraulic system every time the car is driven!
b) Hydraulic Fluid Contamination: The primary contamination factor is from humidity. It may not be obvious, but water contamination from moisture in the air is picked up on the internal extended ram cavity and introduced into the Pentosin PS fluid through the seals. Water decomposes organic hydraulic fluids as well as seals and corrodes internal metal components. Water molecules can diffuse through hydraulic hoses and age seals. Contamination also comes from internal moving parts that wear. Microscopic metal particles wear the seals and adjacent metal surfaces. Being a closed system, (no dipstick, no reservoir, no drain plug) the fluid was never intended to be changed.
If you ever consider a “professional rebuild” of your hydraulic system: 1) insist they supply and wire up microswitches on BOTH rams and 2) make SURE they rebuild the ram plungers adding new seals inside the permanently sealed units!
Don’t wait for a failure – eRam Kit, easily the best value
A new factory system costs $2300. Replacement by the dealer is $3000 or more ($4900 for the 997 Turbo!). The factory kit can be rebuilt or replaced, but the root cause problems will NEVER go away. It was a poor design from the beginning. THERE ARE FAR TOO MANY THINGS THAT CAN FAIL. Even “professionally rebuilding” can NEVER fix the design or potential problems.
Why risk corrosive Pentosin PS fluid leaks into your engine compartment or down the back bumper?
Lighter / Faster / Higher / Simpler / More Robust / Easier to Maintain / Better Downforce
This site is in no way associated with Porsche Cars North America, Inc.
Porsche is a registered trademark of Dr. Ing. h.c. F. Porsche AG.