Rob Edwards

Bob-

It's all coming off, today. Axles are out, e-brake is out, calipers are off, crossmember's ready to drop. I just ran out of protected time till tonight, but the drop is easy. Lots to plate!

928 at last

OK, this is one of those cases where search is your friend, (If it's working).... Just some notes though..
The methods suggested without the use of the Hammer function have worked just fine for me.
I went with the Castrol GTLMA. The others are just about impossible to find in Canada. (And I have a long standing affinity for Castrol products in any event).
The dark spot remaining in the bottom of the res. is most likely the built-in filter (Yep, just like the Power Steering res.) and it's likely loaded with crap.
Testing - I've found a wet road the best test bed. Punch it. The green light comes on and the car straightens out...next question?
This was one of my first projects with the car, and I'm happy with the results. Resources as previously mentioned. Particular care on the cycle time with the pump is advised. (As set out in the write-ups).
Managed to source a replacement res. from Roger, and this will be installed next time around to clear up the filter issue.

928 at last

"nother note....Rob, trust me, what came out of yours was nowhere near the &^%$^#^ that came out of mine. I (IIRC) went through probably a quart and a half of fluid before I was happy with the output. (I think I just dated myself with the imperial measurement).

deutschmick

I flushed the PSD on my '91 GT a little over 2 years ago and put in Ate Super Blue (I had a lot on hand at the time). This thread has me a bit concerned that I should have used the Castrol LMA GT fluid.

I live in a relatively dry climate so that should help <rationalizing>. Is the Castrol significantly less hygroscopic than the Ate fluid? If so I'll change it soon. Thanks.

Rob Edwards

Only took me 6 months to get around to bleeding today.

I R&R'ed the reservoir and bled the PSD on the GTS today. Coupla notes:

Starting point:



Res unbolted:



I dremeled off the old crimp clamps and replaced the reservoir- discovered that I'd ordered only half the crimp clamps I needed. There's a overflow (return?) hose on the reservoir lid - 999 512 527 00 is the clamp for that hose. I forgot to order 999 512 532 00 for the two blue hoses on the res. Oh well. I ended up using 13mm hose clamps:



I splurged on a pair of Knipex 1099a pliers for re-crimping the Oetkier clamps on the inner fuel pump hose, they came in handy here:



They make getting a good crimp easy peasy:




New res in place:

Then proceeded to bleed the system. The only catch is that the electrical system on the GTS is totally dead, so I ended up using my 12V power supply and some test leads to power the pump and the slave solenoid. I got a lot of ugliness out of the system:

Lizard928

I see in the instructions that the system pressurizes upto 2600 PSI.

But how much pressure does it take to actually actuate the differential?

As well, teh sensor right above the pump, I am assuming that is a pressure sensor which tells the pump at which point to turn on/off. Correct?

How much power does the motor produce?

Tails

Colin,

The pressure on/off switch is located just above the pump and is adjacent to the pressure accumulator in the same casting. If you have a copy of PET you and see its location. The system operate between 14 & 18 bar.

I would suggest the force required would be confidential to Porsche, however, to work out the pressure applied to the lock system you would have to know the diameter of the high pressure slave cylinder piston, multiply the developed piston area by the 18 bar and then transpose this force to the lever arm taking into account the fulcrum lengths to ascertain the maximum force applied the regulable plate clutch. As the system operates between 14 and 18 bar, the calculation at 14 bar would be more appropriate to ascertain the approximate force required to generate sufficient friction within the clutch plate to ensure lockup.

With regards to the power used by the pump motor, multiply the volts by the maximum amp draw and you will ascertain the watts (volt-amps) consumed.

Tails 1990 928 S4 Auto

Lizard928

Sorry, I was more interested as to if it was a 1/8 HP etc.

And the writing by Louie and John state a pressure of upto 2600PSI or 180bar.

jeff spahn

Rob- I saw in your earlier (2006 or 2008 maybe) you epoxied painted your garage floor. Howz that holding up for you. I am on my second painting with the "no lift" paint in 8 years. Etched the floor and everything. Still comes up under the hot tires.
Prolly gonna have someone come strip and and do a professional job like a auto shop would have or put down the tiles I have seen in Sporty's catalog.

Rob Edwards

Jeff-

It was an option when the house was new, I had them do it before we ever moved in. So far it's been flawless, holds up to jackstands, solvents, etc.

FWIW, the motor draws just over 4 amps when pressurizing the accumulator.

Tails

Colin
I calculate that the HP is about 0.065 or 1/16 of a HP
Tails 1990 928S4 Auto

Randy V

Can I use Super Blue DOT 4 fluid?

Rob Edwards

You can (I have before) but I think that Castrol GT-LMA is a better choice. Reasoning is here:

https://rennlist.com/forums/928-foru...hing-else.html

WallyP

You can - but I put Castrol LMA in mine. It is supposed to have the lowest susceptability to moisture adsorption of any brake fluid. You will never get the fluid in the PSD hot.

WallyP

Wow! You're quick, Rob!

At least we are consistent.