Rob Edwards

Finally got around to doing the PSD flush today using the protocol of Ott and Veninger. This was really a very easy thing to do and quite satisfying, as the pictures will show. It was also my first workday in my revamped Garage Majal, where I can actually work on the shark inside my own garage.

The instructions are exactly right on all accounts, I had to run to Sears to buy a 7 mm open end wrench for the PSD valve slave cylinder bleeder, and I used almost exactly one quart of Castol GT LMA fluid.

Here's the before shot, note how low the fluid level in the reservoir was, and how discolored the fluid is:



Here's what my factory PSD fluid looked like, keep in mind it's diluted with a good bit of clean run thru! The first stuff that came out of the pressure accumulator looked like chocolate milkshake, though the 'milky' stuff was just a ton of tiny bubbles. The little clamp kept the end of the tubing within the catch basin. Yuck:



And here's the new garage space, just enough that I can safely get the car up on liftbars. Now there's no excuse not to do the intake R&R:

Lord_Galva

Wish my garage was that clean.

John Veninger

F451

Nice.

And are those carboard floor pads? I use old cardboard boxes all the time. They make for good under the car catch alls for the inevitable spills and grit, and I also used them on the sides of the cars to cushion the old knees and back while climbing under the car.

IcemanG17

I gotta admit factory original PSD fluid scares me....yet one more reason I don't have a 90+......however with the new computer (hammer clone) program it would be easy to change it!

Rob Edwards

Brian-

I was a little intimidated to do this after reading the instructions, but I gotta say it's trivially easy. I spent 2 hours or so (not including the run to Sears), but a good bit of that was cleaning the wheelwell around the reservoir, and digging the slave cylinder bleeder out of the 1/2" of grime that had built up on it (I could barely find it at first- I'm convinced that the first thing I would do were I to buy a new shark would be getting the chassis commercially steam cleaned......) If I had to do it again, I'm sure I could knock it out in 45 minutes or so. Now all I gotta do is find a place that I can actually put the PSD to work......

daveo90s4

Brian, you don't need a 'hammer clone' to change the PSD fluid - all you need is a power source (e.g cigarette lighter) and a wire (fused preferably) and an in-line switch to activate / deactivate the PSD system and to 'bleed' the system. And a bit of help from other like-minded souls. So there really is no need to be put off a 90+ 928 due to technology concerns with the PSD fluid changing (in my humble view) - and no need for sophisticated equipment either. Cheers.

borland

The PSD controller fires the PSD solenoid valve by a pulsed signal with only a 30% duty cycle. To avoid damage to the valve, for the solenoid valve activation and slave cylinder bleed, I'd suggest using the Bosch Hammer or the new 928 Diagnostic tool. Here's an o-scope trace I took on my 90' S4's of the PSD solenoid valve being fired, from a few years ago.



Here's a screen shot of the 928 Diagnostic Tool which shows the available PSD bleed functions.

Alan

Rob,
I know you said it was diluted already - but I have seen PSD fluid that looked much much worse!

Still better out than in...!

Reminds me its been 4 years since I last changed mine....

Alan

John Veninger

You can do it manually. You only apply power to the valve for a few seconds, so there is no "valve damage".

Why spend hundreds of $$ on a tool to perform a simple fluid change when a piece of wire works??

Rob Edwards

I used a 6-foot length of speaker wire with alligator clips on either end to connect to the battery, then clamped the other ends onto test leads from my multimeter. I stuck the multimeter test probe into the female connector, and used the other probe tip to make contact with the male connector. The slave cylinder would run for less than 7 seconds before it would stop by itself (as the accumulator pressure drops off), maybe 4-5 sec.
The only other thing that was different in my case was that the resistance on the connector to the slave cylinder solenoid was about 3.5 ohms instead of 2.4 as per the instructions. I must have dirty connections at the solenoid.....

Ispeed

Which is better, PSD vs LSD. I have heard valid arguments for each, and that PSD can do more than LSD (0-100% vs 40%).
Performance-wise? Anybody have track time with both? What do they do differently at the track?

LSD minds want to know...

Randy V

Can you post the link to the PSD flush procedure?

Thanks.

Rob Edwards

Randy:

It's hosted on the 928intl site:

http://www.928intl.com/repair/psd1.pdf

FlyingDog

Mark A. uses GTS trannies converted to LSD. I think a few other do the same. I've heard comments from some street driven 90+ cars that they'd rather have LSD. I've never heard the opposite.

You can rebuild the LSD to any measure of lockup you want. Early units were built as 80%.