Randy V

I was taking a corner at speed when I suddenly lost power steering.

Checked fluid level - was a bit low, maybe 1/4 pint.

Topping up did not correct the problem, so bought a new pump from 928 International.

I'm thinking this is the original pump - 220K miles on the car.

How many of you have had your PS pump fail?

dcrasta

That seems like a lot of miles to me. Have you been replacing the reservoir / filter regularly ? They last a long time when you replace that filter on time.

dr bob

Randy--

The lower pressure pumps are rebuildable. Check with Rennbay and see if they have the bits for your higher-pressure pump. Generally they last a heck of a long time, close to forever -IF- fluid is maintained clean and full.

IIRC, reserrvoir/filter and unit flush every 30k, easy at the same time you do the auto trans services. Already a mess and already have the fluid out, so why not?

Randy V

Where is the filter located?

I've never replaced it.

Lizard928

Filter is integral to reservoir, so you need to replace it. IIRC they are around $17.

I've seen a couple fail, but the rate is pretty low.

kelanel

built into the PS resevoir. roger sells them for around 20-25 IIRC might as well replace the suction and return hose while you are at it.

Speedtoys

Question:

I have an 88 S4, do I have a low or a high pressure pump?

Whats the operational difference between the two as a driver?

I could assume "more assist"..but I would rather not assume.

Bill Ball

High pressure started in 90, along with a revised rack. I can tell you from direct experience with Nicole's 91 S4 that the rack makes a substantial difference, but you will not be able to find the later rack anywhere but from ZF or Porsche and they demand a late rack core. You can try a high pressure pump, but without the later rack the impact on steering effort is reduced. When Nicole replaced her original rack with the commonly availlable rebuilt (earlier model year) rack, it became noticeably harder to steer in parking lot manuevers, despite the high pressure pump she had. It was only after she located a later model rack that the original steering effort quality returned.

I believe the steering effort required in my 89 at slow speeds has increased. I may rebiuild my pump soon or swap in a low mileage spare I bought a long time ago.

dr bob

I suspect we should be out shopping for used racks from cars that came with similar ZF racks but easier steering. Grab the spool valves from them to make our high-effort 928's more docile in slow traffic. The key to apparent steering effort is a little torsion bar spring inside the spool valve on the pinion. Weaker spring equals more/sooner assist from the hydraulics.

svp928

Funny story- I noticed at a track day that my steering would get really hard when making fast corrections- like when you are 90deg from desired direction of travel! and you try and save it..-- then a short while later, started hearing a growling, whining noise from the vicinity of the pump. Car sounded like it had gear-drive blower on it. Several people asked me if that was true...sadly, I checked, and no blower...
So, I got a pump from 928 Intl and installed it. Now, I had NO assist at all, and the growling was still there...crap...heavy sigh. Turned out, the growling was a bad alternator bearing, which, coincidently, is in the same vicinity as the now non-power steering pump.....so, I replaced the alt with Delco (Separate thread for that) and BOOM, no more growling. Then, on the windy road home with new silent alternator, the steering assist magically re-appeared! Cheers and joy.

Bottom line- if you think your steering pump is bad, put an alternator on it....that took care of it all for me.....

Steve

Speedtoys

Is the spring accesible? Could it be weakened, replaced?

the flyin' scotsman

Filter is built into the reservoir..........roger sells
Pumps are rebuildable..........Roger sells

the high pressure years have different pumps, console, hoses and rack...........big diff between S4 and GTS

James Bailey

The PS pump has a blowoff pressure relief piston valve with spring tension. Some rebuilders will shim the relief spring to up the pressure. If under high RPMs the pressure relief opens and STICKS open at low engine speeds you will have little assist. The down side of higher pressure is you COOK the fluid.
In fact, Caymans when tracked have a nasty habit of overheating the fluid to the point that the reservior (plastic) fails and dumps ATF all over the engine and can cause a very nasty engine fire. Cayman R has a cooler !! Late 928s have a cooler loop to throw of some heat.

dr bob

It may be. The spring lives in the middle of the spool valve that's part of the pinion assembly. The top section gets input from the steering wheel, bottom is the pinion that moves the rack manually. You'd need to disassemble that pinion assembly, split the upper section of the valve from the bottom to get to the spring. Delicate work. There are position limiters that allow you the manual steering option on hydraulic failure, but generally the pinion itself does almost no work when the hydraulics are all working correctly.

It might be easier to find a ZF rack from an easier-steering car and pull the pinion assembly out to put in the 928 rack. I'd be looking at 80's - 90's big BMW and Benz sedans. Shop rebuild kits first to narrow your boneyard searching to ones that use the same pinion seals.

wg928

I bought a rebuilt pump from 928 Int'l due to groaning noise....after install the noise stopped however I now have alot of difficulty steering at low speed/parking.....I called and my supplier told me his rebuild may not have good output pressure; I'm about to return that thing shortly and hope I'm refunded.