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by: lnengineering
Description: Article adapted from Marc Gamora's original article Do you find you are having consistent problems with power-steering fluid boil-over and pump cavitation? You may not even be aware that its happening until you see the drip make it to the floor, or have a steering groan and, at times, high steering effort ? Maybe you seem to have to add steering fluid often despite evidence of a leak. The case webbing has a tendency to catch a fairly large volume of fluid, which often doesn’t make its appearance until enough has accumulated and aggressive driving puts it over the edge, literally. Naturally, the high revs associated with track events and autocross result in very high P/S pump speeds, fluid velocity, and fluid pressure. Also, consider that there is an increased demand for power steering assist, as well as more feedback from the road or track. Most importantly, is the increase in both operational and ambient temperature and the resultant fluid expansion, hence the expansion tank, and overflow tube –which is often wet, even under normal use. However, it is usually track use that pushes the system to its limit: the fluid boils over, the level drops thus the pump cavitates, and the high pump speeds whip the aerated fluid into an expanding froth. The mid-engine cars seem to be more prone to it, possibly due to the fact that the steering fluid lines are positioned more closely to ambient heat sources. Some say that “sawing at the wheel “ can exacerbate the problem, and I don’t doubt it. However, it can still occur even with the smoothest of steering input. Not surprisingly, the GT3(and 911 Turbo) doesn’t seem to have this problem -it has a much larger drive pulley, an appropriately valved P/S rack, a robust pump, and an aluminum reservoir. Excessive bump steer can also contribute and may damage the rack and/ or pump. There is a check valve/flow control orifice installed in the end of the pressure line where it enters the rack. I have seen this device damaged and even turned sideways in the bore from pressure spikes resulting from wheel impact-an extreme form of bump steer, right !! When this happens, the pump screams without any steering, and there is no power steering assist at all. On the other hand, low fluid level usually manifests itself as groaning as the wheel is turned away from center, and there is still some assist. Obviously, a power steering cooler will not remedy the former condition. A cooler will help abate the boil over problem when installed within a system that is in good working order. It’s not a cure, but a prevention. Combine a cooler with an underdrive pulley and the use of an alternative P/S fluid for optimal results. Due to shrinking budget, I first tried the cheapest of solutions-a catch tank. Sound principle, but what I found was that the bulk of the overflowing fluid was not making it to the overflow hose, although it was “wet”. Most of the fluid had breached the o-ring that seals the connection between the upper and lower reservoir and the reservoir cap itself. The o-rings were new at the time I installed the catch tank. After dutifully cleaning the affected area, I refilled the reservoir, and bled the system of ingested air. Bleeding is easy and I’ll cover it at the end of the install procedure. By the way, the Pentosin steering fluid used by Porsche (Goo 2000 for VW folks) is aggressive to many types of rubber and plastic, as well as paint and other coatings. The factory service manual advises the immediate cleanup of any spilled P/S fluid, with soap and water. The current factory fluid is Pentosin CHF 202. It is fully synthetic and can be mixed and used in place of the Pentosin CHF 11s. It’s not compatible with systems using CHF 7.1. I can testify to its effect on rubber cooling hoses, especially when it seeps into the cut ends of hoses at their connection points-can you say swollen? It is important to clean it up quickly and completely. Also,we have also found that the factory fluid does slowly evaporate. Many Porsche and VW technicians have noticed this and after having checked comprehensively for leaks, have stopped wondering where the fluid has gone. We’ve changed away from the Pentosin line and now use Redline Synthetic P/S fluid because it is less aggressive to plastic and rubber and has higher viscosity at operating temperature and a higher boiling point. It is also miscible with the residual amounts of Pentosin left in the system. Remarkably, the pump has proved itself very resilient. Prior to installing the cooler, it had boiled over several times, and definitely made plenty of horrible noise. By the 4th or 5th time, I figured it had given up the ghost. However, I gladly report we are still using the same pump, and after the cooler installation we have had no problems to date. This may not be your experience. The pump isn’t easy to get to, and replacing it on a Boxster or Cayman isn’t the easiest job I’ve ever done. Even so, it’s not terrible and I would still rather replace a P/S pump than get a root canal. One area that can leak when the system has been hot is the o-ring that seals the connection between the reservoir and the pump. It really can’t be seen w/o removing the assembly. Excessive temperature can melt the reservoir and deform the plastic, so I guess it is really not o-ring failure, but instead, reservoir failure. The return line into the reservoir is not a common leakage point, it is locked in place with a swage collar and is sealed by an o-ring. Do make sure it is fully seated and locked by pressing it in the direction of the pump and then pulling it away firmly w/o depressing the collar. After ensuring your system is in good working order, you are ready to install your cooler. Perhaps you’ve already considered it , but really aren’t sure where to mount one.I assure you that the installation is easier than reading this article! Here is the procedure:














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