mdss6

Greetings. I'm attempting to repair the malfunctioning pump for the PSD on my 90 s4 (auto), and am wondering if anyone knows if replacement pump parts are available? As usual, the PSD did not get regular fluid changes/flushes, and the 6mm ball bearings corroded and got stuck in the cylinders in the pump. Thus no pumping occurred even when everything else was working.

The pump is out and apart, everything has been cleaned and new 6mm ball bearings are in the pump. But after a brief period of proper operation they keep getting stuck in the cylinders, resulting in the electric motor spinning freely but no pressure.

Since everything else seems to work, the optimal thing would seem to replace the spinning metal parts in the pump with new ones (that ideally work). Is this the common failure mode of the pump? If the pump innards are not available (I'm not holding my breath here), can anyone suggest an alternative short of a $1500 rebuild?

Finally, I should mention I'm not 100% sure it is back together in the right order as I failed to observe how everything was put together when it came apart. Does anyone know of a diagram of the innards of the pump?

Thanks!
Christopher Moeller
90 s4

John Speake

If you are in the USA, Roger Tyson acts as your local agent for a PSD repair service in Europe.

ROG100

Christopher,
I have a rebuild in stock on an exchange basis.
Drop me an email Roger@928sRus.com
Roger

mdss6

Roger,

thanks for the reply. Is the rebuild for just the pump, or the complete PSD? Something in between? What's the price? Everything besides the pump components seem to be working, so I'm trying to limit replacements to that level.

Thanks!
Christopher
90 s4 (Auto)

ROG100

Hi Christopher,
My price is $1350 for the complete rebuilt PSD with a core charge for the return of your old unit for rebuild. These are completely rebuild units and bench tested by the rebuild company in Germany.
The pump alone will cost you $1200.
Roger

Herman K

If it works out that you need a rebuild Roger is your source - Did you run it through the test cycles with a Bosch "hammer" before coming to that conclusion?

mdss6

Herman,

thanks for the input. The Bosch hammer has never worked with my car unfortunately. Diagnosis was instead reached by checking the functioning of each component. The ball bearings getting stuck in the pump cylinders is certainly a problem (through multiple iterations of assembly, disassembly, polishing and rechecking they initially move [pressurizing the system] but eventually [10's of seconds] they stop sliding and thus stop pumping), even if there are others. But everything else seems to be functioning properly.

Barring other suggestions, I'll keep trying to get the ball bearings to slide freely. Can anyone confirm for me if there are any other parts inside the metal pump body beside the 2x 6mm ball bearings and the 2x hollow pistons w/ a bronze ring at one end? If there was a spring to push the ball bearings back out (after being pushed in by rotating against the eccentric surface) it would seem like that would help the functioning? But I didn't see any springs when initially taking it apart?

Thanks,
Christopher
90 s4 (Auto)

Herman K

I don’t have any drawings of the PSD unit it self but I assume that you have a copy of “WKD 496521’ (Service information for the PSD)

The likely hood that some one took it apart before you and a spring is missing is in my opinion very small. I think you should have pursued to get the hammer to works before taking it apart. During my last system flush I had to repeat the transfer lock (hammer test cycle) several times before it started to work properly.

Best is to come to the OCIC meeting in Dallas this weekend and brain storm with some 100 plus owners there ‘m sure you’ll find an answer for your problem than.

Good luck

mdss6

Herman, thanks for the additional input. I do indeed have the service info for the PSD, just looking for some extra detail.

Several service shops have looked at my connector problem for the Hammer, and haven't been able to figure out why it won't talk to my computer. May have to replace the whole cable? Until that is solved, I nor a shop will be able to use the Hammer to help in this repair.

Roger - do the rebuilt PSD's come filled and primed? Is the Hammer / professional-install required to get it up and running, or do I just bolt it on, fill, and go?

Thanks!
Christopher
90 s4 (Auto)

Herman K

I went trhough the experience of not seeing my airbag system with my hammer until I found out that my airbag control unit was bad (when it was replaced the hammer saw it and everythin airbag has worked since) In you case the the additional platinum board in the ABS control unit may be bad and that's why the hammer doesn't see the PSD system? (WKD 496 521 page 4-3) I'm saying you the hammer needs to see the system first before you come to the conclusion that yours or a replacement unit will work.

I guess best checked by swopping an ABS control unit first before anything else.

ROG100

Its a bolt on fill and go.
You can operate the PSD without the Hammer - just not that easy.
Bring your car to the OCIC and we can check it out for you.

SeanR

I'm going to guess that the reason the hammer won't work on the car is due to it being chipped? Do you know if the computer chips in it are stock or aftermarket? It is possible to bleed the PSD w/o a hammer but it is not exactly easy. You will also want to ensure that it is bled properly also. Bleed screw on top of the unit that you can see, and one on the passenger side/top of the transmission.

I personally would not do it w/o the hammer, but that's just my .02.

John Speake

If the Hammer does not pick uip any fitted ECUs then check fuses #25 and #41 which power the diagnostic connector.

Even if the LH or EZK have chips that won't diagnose, the Hammer should still recognise other ECUs.