merchauser

^^^^ fred, not sure how I can isolate certain passages with everything apart. I imagine, that in order to test properly, I have to install the plug for the check valve?
with that in place, I attempted to blow air thru the hole in the pump, but could not get any air thru the hard line hole, or the accumulator hole.

can you suggest a better method to test? or perhaps, the check valve needs a great deal more air to activate?? remember, with the PSD in the car, I pulled 25" of
vacuum thru the solenoid bleeder and could not draw any fluid, and the needle on my gauge was rock steady at 25

merchauser

are these all the parts found inside the pump??

FredR

If the check valve is spring loaded then the vacuum may not be enough to open it. Pressurising the check valve from the inlet side should get it open easily enough unless it is seized shut.

Unfortunately I am not familiar with the construction details- a sectional drawing would be useful were such available.

GregBBRD

merchauser

showed the pump to a local small pump specialist, and although he is not familiar with the PSD, he has 50 years experience in small pumps.
his OPINION is that the pump is fine, and the issue is air lock.

I was thinking bypassing the reservoir, and pressurizing fluid directly into the feel hose at the pump, capping the check valve, and capping the port
for the accumulator. hopefully this would break the air bubble and force fluid thru the hard line orifice.

sound good, or does someone have a better idea??

FredR

Brave man pulling one of those things apart!

There should be an "initial charge" procedure somewhere but where? It must have been done plenty of times and if a vac on the outlet bleed does not do the trick then pressurising the reservoir to say 15 psig ought to be viable assuming the reservoir is mechanically up to it. Pumps of this kind displace very little volume as their mission is to achieve the high pressure needed so not too surprising that they might be tricky to bleed when one thinks about it.

Assuming you manage to get it all back together again and working, make sure you have goggles on before powering it up. If the thing is leaking they can squirt brake fluid the length of the garage before you even know what has happened .

jcorenman

No, the green thing is the pressure switch and the threaded plug hides the check valve.
Everything else is the pump: The two pistons and ***** go into holes in the hub, which goes onto the (stationary) shaft with the ring-thing around it, and then the plate goes in (oriented correctly).

But from where you are, with the motor removed and looking down into the pump, just fill the pump with brake fluid and try to reassemble without spilling (much).

merchauser

ha ha fred, the photo with the pump disassembled was from jim corenman; I have not taken the pump apart and there is no need.
I did take off all the other bits. will keep goggles handy!!

SeanR

Same.

No need to use a power bleeder or anything else. If the pump and assembly is working all you need to do is fill it up with fluid and run the bleed sequence either with the hammer or the key on method. Once the pump is not shooting out any bubbles then go to the slave and do the same thing. Once that is done I go back to the pump and re-bleed, slave to re-bleed it, it to ensure no bubbles and call it a day.

G8RB8

Try taking the bleed nipple all the way out. It could be clogged.

merchauser

sean, in the past, I have followed the Ott method to bleed the solenoid, and the hammer to bleed the slave. can you tell me how to use the hammer to
bleed the solenoid?

my problem has been that I cannot get the pump to prime; I can say with near certainty, that my pump and motor are fine, and the unit was darn clean before
I took things apart, and now it is spotless.

G8RB8, thanks for the tip. the bleeder was clean, and the entire unit was extremely clean to begin with, but now is even better.

FredR

Paul,

Well you sure fooled me!

Interesting how in this thread we have Jim and Sean stating two diverse opinions about priming of the thing. Read a little deeper and saw Jim's reference to a previou thread- opened that and see GB stating they can be difficult to prime- I'll leave it to those wise chaps to beat the poo out of each other on that one!

Baffled as to how your pump expert friend can determine the condition of the pump without disassembling it. I guess the $64 million question is how long did the pump sit dry and how long was it trying to operate in such condition. Not sure what the diagnostics tell the driver other than "PSD non functional" or whatever the wording is. If there is an alarm condition I would hope that it will not permit the pump to run [a start permissive] but I do not know that. I find it frustrating that such info is not even in the WSM's- that or I have not found it!

Bottom line if the thing is viable hopefully you will get it sorted but when these things play up it seems to me that there is little in that thing that folks like ourselves can do to rectify the issue. I suspect the poor thing will be vulnerable to the same problems brake systems face if the fluid is not changed regularly. As you will no doubt be aware brake fluid is [generally speaking] hygroscopic [i.e. it absorbs moisture from the air] and that moisture can create chaos which I suspect may have been part of the problem on the unit Jim pulled apart if a PO did not do what was needed. Even my unit which I flushed a couple of years ago [and had the main agents flush previously] had clear fluid coming from the main cylinder but the stuff that came out of the diff bleed was murky to say the least. I reckon the fluid should be flushed every 3 years and if one is going to be really **** about it - every two years.

merchauser

not my intent; wanted to confirm exactly what was inside, to show the pump man.

agreed and noted. he examined the photo of the inside, spun the pump, and put it to his ear (similar to a psychic) and I clung to his OPINION like a
drunk to a gin bottle. he strongly felt that the unit was air locked.

for those interested, here is the complete text from the WSM: I have made notations in red

Bleeding hydraulics of Porsche controlled slip differential (PSD)
Remove rear left inner fender
Connect bleeding device to PSD hydraulic reservoir . no photos, but first thing they recommend. hmm
Disconnect vent line
Build up bleed pressure (approx. 1.5 2.0 bar) disconnecting the vent line and pressurizing to 21 to 30 psi is a big mistake!
early style reservoirs have a vent nipple on the body of resv., while later ones have vent on the cap.

1. Bleeding the pressure reservoir
To charge the pressure reservoir, the ignition must be switched on. When the pressure reservoir has been charged, the pump cuts out; reservoir pressure is then approx. 180 bar. (2600 psi)
Connecting the bleed cylinder. .
Switch off the ignition. .
Carefully open the bleed connection and allow the pressure level to drop gradually. While this is being done, the ignition must remain switched off, to ensure that pressure is completely reduced and air expelled from the reservoir. .
Repeat this procedure several times, making sure that the ignition is switched on or off at the appropriate stages in the procedure.
no mention of hammer use for this initial procedure

2. Bleeding the valve block and the locking line to the lock slave cylinder
Connect the 9288 system tester bosch KTS or hammer tool
Switch the ignition “ON”
Connect the bleed cylinder to the bleed screw on the slave cylinder
Open the bleed screw on the slave cylinder Select “Start PSD Bleeding” and actuate repeatedly until no further air emerges
The bleeding device must remain switched on, because the reservoir volume is used up rapidly,
After this, close the bleed screw on the slave cylinder
Select “Stop Bleeding” and “Start Pressure Reduction” at the system tester
Switch off the bleeding device and disconnect it
Screw on the reservoir cover
Open the vent line at the reservoir again
Check level in reservoir. The liquid must be approx. 1 cm above the step in the reservoir body (with the pressure reservoir charged)

This is all the WSM provides ????? no photos and no mention of priming pump??

AGREED! as mentioned, my PSD was flushed earlier this year, and it was nice and clean, and PSD pressurized and worked fine. only took it apart for this
drip leak, which the motor seal replacement solved. that is why i feel pretty good about the health of the system (it was out of the car for 4 months)

Sean, let me know how to use the hammer for the bleeding of the solenoid; maybe this is a tip/trick that could help.

GregBBRD

About out of popcorn.

You guys going to figure this out, or not?

merchauser

one thing I find strange is that the orifice for the plastic elbow that feeds the pump cavity, also appears to share the path
that the pump supplies to the check valve.

that would mean, that the pump will push fluid up towards the check valve, and could pump fluid back towards the reservoir,, as well.

this doesn't make a much sense?? is there another orifice behind the plate which covers the ball bearings?