Low speed steering noise

[henry997]

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.

Henry

 

[Big Dave]

In my opinion its a 944/968 character, of weather RHD or LHD, i think most do it...

 

[Chrishazle]

Mine certainly does - and has from the day I bought her. I was told by OPC Tonbridge (where I bought her) that it was a 968 characteristic and not to worry about it - so I haven't!

 

[David Hooper]

I thought it was just my old one but.......the new one does it too[]

It's a feature, we're not sure what the benefit is[&:]

Cheers
Dave

 

[Super_Marv]

ORIGINAL: henry997

Any hints on cures or fixes short of steering pump replacement gratefully received.

Check the colour of your powersteering fluid. IIRC, it's supposed to be a cherry colour. If it's brown or black, it's time to replace your powersteering fluid! I think old PAS fluid can make the pump noisy.

 

[Paz]

I use Castrol ATF DIII (circa £7 for 1L) fluid in mine, I think so long as it's Dexron II or III and red in colour it should be fine.

 

[henry997]

Just had the power steering fluid changed and the system flushed through. The Result ? ........ No change. Might even be worse !! Hmmmm.

 

[Neil Haughey]

I have always thought it must be a bush somewhere, both my S2 and 968 do it at parking speeds but it doesn't seem to make any difference. Wait until you start getting a squeaky sunroof seal or hatch, that can drive you nuts.

 

[henry997]

Its the last "rattle" in the whole car. Otherwise perfect. I have to believe someone at Porsche knows the answer. Seems a common enough problem but always met with a shrug. I feel a mission coming on!

 

[Big Dave]

Henry.
If you do get to the bottom of this noise, itl help a lot of 944-968 owners out.[][][]
As weve got used to "living with it"...

 

[henry997]

I had a response from a Rennlist member

"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."

Am also continuing to investigate with some Porsche technicians.

 

[henry997]

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.