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Power Steering Pump Cutout Fix FAQ

The idea:

Speed sensitive steering is a feature available on many different cars. Its job is to give the car a more stable and heavy feel at highway speeds, and to make the car less prone to sudden changes in steering angle at speeds where such a move would be dangerous. It also allows more steering assist at low speeds for parking maneuvers.

The Problem:

Speed sensitive steering is great, but that's not what our 2L (Turbo&NA) DSMs are equipped with. We have RPM sensitive steering, which acts somewhat the same. It will decrease the steering boost at highway speeds because the engine is turning 3500-4000 RPM, but unfortunately it severely cuts the steering boost in the upper-rev range, regardless of what gear the car is in. 6000 RPM through an auto-x slalom results in minimal steering assist, followed by a sudden lack of any assist. Not exactly what an auto-x driver is looking for.

The solution:

The steering assist reduction is caused by a valve in the power steering pump itself. We will be adding a spacer to preload the spring inside the small assist varying valve that closes at high RPM. This will stop it from restricting the flow of PS fluid out of the pump at high RPMs, but will not raise the maximum pressure of the fliud leaving the pump.

Some people have in the past shimmed the flow bypass valve in the pump. This is a separate assembly that sits below the assist varying valve. This resulted in more steering assist at high speeds, but accomplished this in a bad way. The flow bypass valve is there to relieve the high pressure created when the pump spins faster (high RPMs) and the flow exceeds that which is needed by the power steering system. If you shim this valve the fluid has nowhere else to go, and its pressure will increase far beyond the factory levels. I tried this, but after a 15 minute drive at moderate speed my fluid boiled and I lost steering assist. Not good.



Procedure:

You will want to figure out a way to either drain the power steering reservoir or divert the flow of power steering fluid around your alternator into an oil change pan, as a significant amount of it will flow out of the top of your pump during this fix.

Warning: This modification may change the way your vehicle reacts to steering input; perform it at your own risk. I personally found it made very little difference in the steering response during normal driving, and was only noticable during extreme maneuvers. It should not cause premature wear of any parts of the power steering system. Your mileage may vary. There has recently been a report by a member that the pump in his 92 turbo isn't the same construction as the unit in this FAQ. Anyone want to second that?

Written by: Matt Price Last updated: 12/22/99 Comments? E-mail me at LIL4X4@Hotmail.com

    1. Remove the nut indicated by the red arrow, and pull the metal line off of the pump over the exposed threads.

    2. Remove the threaded fitting indicated by the red arrow (shown removed). I unscrewed it with an allen wrench through the exposed flow holes.

    3. Loosen the large, thin exposed hex; it is the assist varying valve assembly. Pull the whole assembly out.

    4. Here is shown the removal of the flow bypass valve, you can pull it out with a magnet. I removed it to inspect it, but removing it is not necessary for this modification.

    5. Here we see from left to right: Threaded coupling, assist varying valve, and bypass valve w/spring.

    6. To disassemble the assist varying valve, place it in a large deep socket (or something similar) supported somewhere on its outside diameter, not by the small dark colored cap at the very bottom. Put a long thin screwdriver through the threaded hole in the top until it hits the bottom - make sure it goes all the way down. Tap the screwdriver handle gently with a hammer (or vise grips, or a ratchet, or a rock...) until the cap pops out.

    7. Take the spring and plunger out of the case.

    8. Here we see the spacer, which is 3.75mm in length in my case. I made it out of 9/32" thin wall aluminum tubing, it did the trick. The 3.75mm is not an exact requirement, it could probably be a bit shorter and still work fine. I just made it that length because any longer and the spring wouldn't seat correctly in the plunger.

    9. Put the plunger into the case, then the spacer into the plunger. The spring should now seat in the plunger on the new spacer. Now pound the cap back in. Reverse the disassembly steps above to reinstall everything.