Minimarvel

Have a 2007 S8 60K miles, that had developed an annoying whirring noise when moving the wheel. Power steering seemed OK but in fact ( now discovered) it had become a little heavier.
Quiet when first started from cold but got noisy after a few minutes once fluid heated.
Changed fluid, checked pipes and connectors...No change.
Main dealer inspected and said pump was the problem....Engine out job to replace...!!!!

A fair bit of research and a visit to a power steering specialist concurred that for the cost, better to leave it alone until it failed completely, better than a £5,000 bill....

Found the Reservoir and thought that the filter in the bottom might be blocked and "starving" the pump (No air bubbles or anything like that), Changed it, and have the cuts and grazes to prove it.
It did indeed make it quieter but only fractionally...In short, not a fix.

Last ditch effort was to add a bottle of Lucas Power steering stop leak. ALL NOISE GONE....!

Yep completely silent, power steering much much smoother and feels like it did when new.

Just to give you guys a heads up. ......

And, just to clarify, I am an engineer, don't work for Lucas and am probably the most amazed pessimist alive today....

I am guessing without disassembly, that the vane pump wears with time and this wear produces the noise. The Lucas stuff is like treacle and obviously fills the gap.
I put a whole bottle in after syphoning out the reservoir. Instant fix and I did check it was compatible with the G004 Hydraulic fluid which although stable thru the temp range is still very thin at 40 degrees.
Early days but think this might be a thread that could become a sticky, as it seems many people have similar problems on other models, only to spend a fortune on replacing pump and Racks.

Jack88

I'm glad that worked for you. No harm in trying it, since you were looking at replacing it anyway. I hope it holds for you.

Minimarvel

Hi Jack,

I spoke to another engineering colleague this morning about this. Seems the wear on a vane pump will produce this defect after time and indeed his opinion is that the pump will continue to work without failure at a lower output rate even if nothing is done.
Adding a fluid with a thicker viscosity will definately help as long as the viscosity stays within range. Worse case, if the noise returns, replace fluid and additive and another life is added. The unknown at this stage is the time period attached to such a "life".
For now, I am as happy as Larry....

richard-tx

I really wonder what is in that stuff and how it affects the rubber seals of the rack.

Minimarvel

I did research, especially on pouring it into a true Hydraulic system, rather than a Dextron based one. I could not find any negative seal destroying stories. The only explanation I could find was that the seals on the racks, with repeated hot/cold become hard with some shrinkage, hence the leak. This stuff claims to soften the seals and return them to how they were when new. I don't quite get how that works, but as I said, couldn't find any negatives....Just the increased viscosity would stop it flowing thru a seal "gap" I am guessing.

Google is our friend I am told. If anyone finds info, I'd be very interested.

Rgds

Dave

richard-tx

If something goes wrong, then pulling the engine will make pulling the rack and pump easy.

kgd_007

I had two different S8's (2008 & 2009) both enveloped the issue with that steering noise. Nice there is an easy fix.

gregg galletta

Hi there, I just developed a whining noise on my 07 S8 with 80k. Wondering if it's the same sound you experienced? Not sure you're still active here. See (hear) attached. Is this what your's sounded like?

Minimarvel

Not the same noise, but I know that noise.....and the fix.

Jaguar had the same issue once upon a time and they have a product that you add to the PS fluid. Instant fix.
Sounds crazy...but I am an engineer and hate snake oil...

https://www.ebay.co.uk/itm/GENUINE-J...-/332221446386

Regards

David

Mister Bally

Also known as "Technician in a can".