Greeting all:

I'm into alot of things on the 928 right now and I'm getting frustrated.

I removed the PSD unit to clean it and the fender area. I've found two problems

1 - With I turn the key on, there is no power at the hydraulic pump power cable. It is not listed in the fuse panel directory. Any thoughts on that.

2- I attempted to flush the PSD unit following the Louis & John directions. I have the bleeder valve open on the the locking solenoid, but when I apply power to the pump, it runs but does not pump any fluid.

As usual, any help is greatly appreciated.

Tim

 

Tim,

I had a similiar issue with mine when i tried to bleed the system some 6 months ago. I couldnt get any fluid to come out of the lock solenoid. So I then gave up on the idea of flushing it and havent tried to do it again since.

I am curious to see what others have to say about this as well.

 

I've been thinking if system needs little help to get fluid going if it has been dry for a while. Maybe small overpressure applied into expansion tank fillup hole would help?

 

If the pump runs it should cut out when it has built enough pressure in the pressure reservoire.
If it runs but does not cut out it indicates the pump may be toast and unable to build the pressure or pump the brake fluid.
This typically would happend if the pump has been run with not enough break fluid in the fluid reservoir.
Some people says it might help loosen the whole assembly and shake/twist it to help the pump start priming, it never helped on mine.
So I ended up buying a functional second hand unit and it all now works.
(I also followed the excellent write up from Louise and John)
Really hope you can make it work

/Peter

 

Desperate bump

 

It's been over a year ago, but we did it on a GT and 2 GTS's using the Lewis and John directions and it worked perfectly so it's not the procedure, unless your not following it correctly. The shop manual procedure is very involved and requires the use of the Bosch Hammer to command the PSD's computer to move the fluid through the PSD. To flush and bleed the PSD unit without the Hammer, you need to energize a solenoid to release the fluid from the accumulator as well as operate the motor to pump up the accumulator with new fluid. Sorry this isn't more help.

Jim Mayzurk
93 GTS 5-spd

 

Interesting; I just flushed my PSD this past weekend on my 91GT and the Louis/John method worked well. I know this sounds dumb but was the ignition on (position 2)? You also said you removed the PSD unit to clean it; when looking at mine it appeared to be possibly isolated electrically by plastic washers. Could it be grounded wrong? I don't even pretend to know much about electrical problems but hope this might help. Good luck!

 

Just a quick question: when you open the bleed valve, and energize the pressure solenoid, the stored pressure in the reservoir is released into the slave cylinder line and bleeds thru the bleed valve. Thus allowing fluid and air to escape. At what pressure do you guys see the fluid escape thru the slave cylinder bleed valve? Is this like dripping or under pressure? Is this different when using the hammer as compared to the Lewis/John directions?

@Tim: most has already been said: if you apply power manually, you hear the pump run. Fine. If you see no fluid escape from the open bleedvalve on top of the pressure container (!) then it seems your pump is not pumping at all as there is no pressure buildup. On the seperate pump relay unit there is a fuse if you're looking for that one? If that pressure container bleed works fine, move on to the solenoid valve and the slave cylinder bleed.

Theo

 

Question 1. There will be no power to the pump if the system is already pressurized, or thinks it's pressurized. You can also check the PSD relay.


Question 2.
The pump should run until the the pressure switch sees the correct pressure. The solenoid releases the pressure to the slave cyl. which will allow fluid to be released from the bleeder screw on the slave cyl.
So I'm confused when you say you have the bleeder valve opened on the locking solenoid.

Silly question, is there fluid in the system? Does the pump run and then stop? Does the solenoid click when power is applied? Is the bleeder screw opened?

 

Thanks for all the replies.

Currently I have the unit removed from the car and I'm attempting to flush the system. I removed the old fluid from the fill tank and replaced with new. I attached a drain hose to the bleeder screw located on top of the locking solenoid (the square thing). When I opened the bleeder screw the first time, there was some pressure. Now with the bleeder screw still open, I manually apply power to the pump to move new fluid through the system. I can hear the pump running, but no fluid moves.

Perhaps this flush procedure doesn't work if the unit is not mounted in the car with the other cables connected.

 

That is correct, you should follow the procedure from the description from Louie and John with the PSD unit mounted in the car.

/Peter

 

Thanks, I'll let you all know what happens.

 

Referring to Figure 1 on page 3 of the Ott/Veninger directions (layout and editing by yours truly)...

If there is sufficient pressure in the Pressure Accumulator, when you open the bleed screw on the locking solenoid (square thing) (with your bleeder hose connected to it of course) there will be a LOT of pressure (as in "sqoooooooooooooooooooooooooosh!").

Then, after you close the bleeder screw, when you reconnect the two-pin connector to the Hydraulic Pump, with the ignition ON, the Pump should run for 15 or so seconds and rebuild pressure. Re-bleed as above and as described in the procedure.

Once the fluid you get from the solenoid is clear and no longer frothy, you continue with the rest of the procedure and bleed the slave cylinder.

Hopefully, that's a clear summary...

 

Hi guys!

I need help too!

I had some troubles with my PSD on my '90 GT: says "Off" on the dash, no function at all...
I swap it for a used one bought on the german ebay, following Ott/Veninger directions (very good job, indeed ), and still have a non functional PSD, Off on the display, but I can hear the pump working continuously

The question is: whenever I would install a new PSD module, what should I do to be sure that the liquid is REALLY inside the empty new pump when I start it, in order to avoid getting it burned?

Thanks!

Cheers,
Michel

"Drive your shark twice a day, keep the mechanics away!"

 

The only thing I can think of is that either the pump is not generating any pressure inside the accumulator or there is an obstruction that is not allowing the fluid to come out. It might be messy, but you could try slowly disconnecting the hard line from the accumulator to see if there is pressure there. If there is, then there must be an obstruction either in the hard line or in the slave. If there is no pressure, then the pump must be bad.