kevin2012

I notice that my PSD fluid level is dropping and triggers the diff warning message on my dash. I got under the car and checked the path of the PSD hose all the way to the diff. I could not find any leakage.
The PSD pump area is also very dry.
Where does the fluid go? Into the diff?

Thks.

NoVector

It can if your slave cylinder is leaking. It's uncomfortable to get to, but only 2 bolts and the feed line to pull it and check it out.

kevin2012

Is it possible to remove the slave cylinder without removing the halfshaft?

Also,if the PSD fluid(brake fluid) leaks into the diff, it will dilute the diff fluid, do you think that it will damage the diff gears ?
Cheers

NoVector

Yes, the 1/2-shaft can stay in place. There are bellows on the end of the slave cylinder plunger "I think" to stop brake fluid from leaking into the diff in case the cylinder leaks, but I guess it would all depend on the condition of the bellows. I think you'll find this an excellent read:

http://forums.pelicanparts.com/porsc...pair-pics.html

kevin2012

I am getting the PSD slave cylinder and other related items from Roger. Meanwhile, I disable the PSD by removing the relay and the fuse from the spare tire area, unplugging the electric plugs of the pump and the pressure valve inside the rear fender but keeping the Transverse Lock Valve connection in place. By doing that, I got no ABS or PSD error. Now I can still drive my car with ABS on while waiting for the parts. Since the pump is not functioning, I hope the fluid will not have high enough pressure to enter the diff.

When I was disconnecting the soft PSD hose under the car(near the rear muffler) to release any residual pressure , the fluid was dripping a lot and almost empty the PSD reservoir. Is this normal? The transverse lock valve was not activate so it should be closed and should not drip any fluid. Does it mean that the transverse lock valve is faulty?

Thanks.

kevin2012

I think that if the long forgotten PSD is flushed, be prepare that some components of the system will have issues too. Like the soft PSD hoses, the pressure regulator and most seriously, the slave cylinder. If the slave cylinder leaks after flush, the PSD fluid will leaks into the diff. and the diff. oil will be diluted/contaminated and damage the diff. Or if the slave cylinder stuck out after flush, the lock will be always on insider the diff. and the diff. will be damaged too. So if there is a long forgotten PSD, it should not just do a simple flush but a full inspection of every single component of the system otherwise the flush will do more harm than good.
Too bad, I guess I had learned this lesson in a hard way.

NoVector

I’m not sure about the dripping… My $.02, install the parts from Roger and then flush using these instructions:

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

When flushing, I would run at least 3 pints of DOT 4 fluid through it—but 4-5 pints for peace of mind.

In the event everything turns to crap and your PSD needs service, Roger used to provide a core service. And there’s also a guy named Harold Stein here in Germany who can rebuild them. Mine was rebuilt ~3 years ago. His website is: http://www.stein-aviation.de/html/psd_engl.html

You’ve prolyl found that the reservoir (with filter) is no longer available. As an alternative, below is how herr Stein solved that problem with an external filter.

The PSD’s a funny thing. Rather than remove the potato chip thin/crumbly cover during the PPI, because I wasn’t receiving any errors, I thought I’d save it for a rainy day. When that day came, I found all the connectors disconnected, the fuse missing and the reservoir filled with nasty fluid. Somewhere along the line, a PO gave up. So after a rebuild PSD, a replacement slave cylinder and a lot of flushing, it was good to go. Keep the faith… There’s a light at the end of the tunnel and it’s not a train coming at you.

kevin2012

Thanks for the info. and the encouragement.
To start with, I will remove the old slave cylinder and have a look.
The space is quite tight (with the half shaft on) but I guess it is doable.
Also, may I ask the torque value for the slave cylinder bolts? I cannot find it anywhere.
Do I need any gasket or sealant for installing the salve cylinder?

Cheers.

Bilal928S4

Can you tell me where is this slave cylinder in the PSD circuit?

kevin2012

It is located at the right side of the diff. Right above the right side half shaft. Search here in the forum and you can see some pics.
Check everything especially this slave cylinder. Don't make the mistake like I did.

Cheers.

NoVector

I couldn't find the torque either when I did mine. Since they're M8s, I think I went with the rule of thumb 15 ft lbs. No gasket per se--but it does have the bellows. You can see it in the PET (#14). Think of it as a rubber accordion condom.

kevin2012

It was a bit of struggle and fright but finally I was able to remove the slave cylinder. It does not look pretty but it is not stuck.



Another issues is that i can not remove the metal line from the cylinder and the metal line to the pressure valve. If i try harder ,i will round the nuts.

Tom in Austin

I've learned a lot in this thread about what can happen in the PSD system. Possibility of the bellows disintegrating is one I hadn't thought of before ... to go along with a leak in the slave & etc.

mike77

Me too. Dealing with the psd is one of the jobs on my list. It was topped up recently but I don't know when it was last flushed. Some of my lines are showing signs of corrosion. I figured I would replace the lines and do a flush. Looks like there is a bit more too it. Interested to hear how you get on with completing this job.

ammonman

Clean the area where the pipe enters the flare nut on the salve cylinder really well and apply some quality penetrating oil there and to the threads of the flare nut. Let it sit several hours before clamping the slave cylinder in a vise and applying a flare nut wrench to the nut. Yo may need to carefully loosen the nut just slightly before tightening it again followed by another cleaning and penetrating oil shot. Keep working the flare nut a little farther loose each time and clean/re-oil each time. The corrosion often sets up between the flare nut and the pipe so monitor that the flare nut is spinning freely around the pipe and not simply twisting the soft cupro-nickel pipe. If you can't get it to break loose apply some heat to the flare nut to make it expand and break the corrosion.

Mike