Hi,

At low speeds, typically whilst parking, I sometimes get a humming/singing resonant sound from I think, the power steering pump / mechanism. I've been told this is a 968 "characteristic" on RHD cars and never happens in LHD. Is that right? Is there a fix? Is it a sign of a worn seal or is this just the result of a resonant harmonic being produced in the plumbing of the steering assistance system? Any hints on cures or fixes short of steering pump replacement gratefully received. (I have changed power steering fluid but to no effect). This seems to be a common enough problem (944 S2's as well ?) but always met with a shrug when enquiring about a solution. Do any members on this forum know about the problem or can you direct to the right department at Porsche in Germany that may be able to help ?

Regards

Henry

 

Sometimes the fluid suction line gets weak and it gets sucked partially closed, causing the pump to vibrate as it is trying to pull fluid. Check the suction line. Also the fluid reservoir has a filter in the bottom of it, and if it is partially blocked, you will have the same lack of fluid getting to the pump.

 

Thanks Jay, the best (and only) sensible response I've had so far! I have to assume that with you living in St Louis you've encounted the issue on LHD cars which puts paid to the hypothesis that it was only a fault on RHD cars. (I live in London).

 

Yes I have had this on 2 different 944's nearly at the same time. The original suction line on the 944 was longer and traveled through a mounting clamp that squeezed the hose slightly, and over the years this smaller passage weakened and caused problems. The 968 has a shorter, more direct line which may be less likely to weaken but changing that along with the reservoir may just fix it. If you can watch the pump for vibration while someone else turns the wheel you may be able to tell for sure that it is where the noise is coming from. Be careful of the spinning pulleys and belts while you are in there.

 

I have a 1990 S2 (RHD) with the same problem and I too have tried to locate it. To me it seemed to be partially temperature sensitive (it occurs more in winter less in summer) but strangely it doesn't occur all the time.

> Jay W is that filter hard to access? Do you need to drain the reservoir to get to it?

 

Ditto on my 1991 S2 RHD.

Cheers,
Mike

 

Here's an alternative response (edited email thread) from a Technician at Porsche Reading who's been there for 25 years.

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Hi Henry,

Please check the ride heights of the car and then carry out a full geometry, set castor to its lowest figure in spec.The noise that you are hearing is a hydraulic valve resonance inside the steering rack.Setting the castor lower will improve noise but will not cure totally.

Regards John.

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Thanks John,

Really appreciate the prompt response. Will fitting a new steering rack fix the problem or will it still make the noise if the castor is set too high? The noise dosent necessarrily happen at full lock whilst parking. Indeed relatively small steering inputs at low speed also seem to induce the noise.

Regards

Henry

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Its hydraulic resonance past the valves in the rack,when we replaced the rack, the difference is minimal. Check the geometry and what the figures are.

Regards John.

 

The noise was much worse on my cars when it was cold out. Since I had major restriction in my suction line it was a very loud and embarrassing noise, if you only have some restriction it may be less noisy.

The filter is built into the bottom of the reservoir, so replacing the reservoir is the only way to fix it.