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I am going to manual pour fluid into the pump cavity, and then use my motive power bleeder to force fluid in using
the WSM suggested psi of about 30 psi.
here is what I have rigged up to force fluid into the pump and bypass the reservoir to avoid the mess. I bought a fitting
to attach to the motive, with a barb and clamp to attached to the feed hose.
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?
This is incorrect. You are not studying the fluid channels properly. And you need to bleed it with the accumulator on it and best done with the transfer hose attached to the solenoid but cracked loose.
I was confused because that same hole does have a passage that continues up towards the check valve. I assume that orifice is a dead end??
so the feed channel is behind the plate that covers the pump mechanism?
is the main point of the priming to get fluid past the check valve, and is it imperative that for priming (not bleeding) that the motor be energized?
wondering if I can prime the pump using the power bleeder with the motor off?
I was confused because that same hole does have a passage that continues up towards the check valve. I assume that orifice is a dead end??
so the feed channel is behind the plate that covers the pump mechanism?
The hole pictured there connects through to the hose connection that goes to the reservoir and does not connect to any other orifices in the housing.
Originally Posted by merchauser
is the main point of the priming to get fluid past the check valve, and is it imperative that for priming (not bleeding) that the motor be energized?
wondering if I can prime the pump using the power bleeder with the motor off?
The priming has nothing to do with the check valve and the check valve is not causing you any problems. You cannot run the motor for very long and need to monitor the temps so that you do not burn that motor out. It is not designed for continuous use.
Leave the motor off and pressurize the power bleeder will simply result in fluid spraying out of the hole pictured above. Nothing more will happen.
I see an "Internet Myth" forming, here and would like some clarification/background.
This thread is the very first time I've heard anything about the PSD motors failing from overheating.....I've never seen this happen. As a matter of fact, I've never had to replace a PSD motor.
I get lots of vehicles in that have no fluid in the reservoir, can't build pressure, and have the PSD motor running continuously....and have had the motor running for weeks/months. There is nothing, in the PSD system, that will shut this motor off. There's no temperature switch. There's no circuit that tells the motor to shut off (if the system doesn't build pressure) after a certain period of time. There's no "level" switch in the reservoir. There's no protection, for the motor, anywhere. If the motor running continuously was an issue, it seems like Porsche would have built in a "safety" switch, of some sort.
I've repaired literally hundreds of PSD systems. Dozens of which have come in with the pump running continuously from loss of fluid. Never had a bad motor. Not a single one.
I'm just saying that if this was an issue, I'd be seeing dozens of burned out motors.....
I do agree that the motors get pretty warm and that seem too hot when you touch them (when they run continuously), I don't agree that they fail from running like this and getting hot.
SUCCESS; got the pump to prime and have begun bleeding. thanks to everyone who helped, especially, jim, fred, and colin.
jim suggested that I fill the pump cavity and hold the unit upside down to get the flow thru the channels towards the accumulator.
next, I attached the motor, and pressurized to 30 psi. energized the motor, and in less than a minute I was getting gurgling and then
fluid from the orifice where the hard line routes to the solenoid. bolted PSD back in place, connected the plugs, and all good!
while I had everything apart, I replaced the O rings for the accum, check valve, and the pressure switch. accum and valve O rings were fine,
but the pressure switch O ring was hard and needed replacing.
I have bled the solenoid successfully, but not sure about the slave. using the hammer, I am able to pulse the solenoid, but the flow is
small, and is in sync to the pulses. is this correct? or should I be getting a consistent higher pressure steady flow, similar to the solenoid?
here is a repeat of the WSM instructions for bleeding the slave. they mention attaching a bleeding cylinder and for it to be switched on.
is this a suction devise? can I/should I use my mity vac? what is this bleeding cylinder?
. Bleeding the valve block and the locking line to the lock slave cylinder
Connect the 9288 system tester (hammer)
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 (???)
Last edited by merchauser; 11-12-2018 at 08:35 PM.
I have read those articles and realize I don't NEED to use the hammer, I just happen to have one, and it does make it easier to bleed the slave
since it automatically pulses the solenoid, and then has a pressure reduction option.
Jim Corenman has schooled me, and now i know that the flow at the slave should be pulsed in sync with the solenoid. that is happening and all good.
my concern now, is that the flow, during those pulses is inadequate, and I wonder if there is a blockage. fluid coming thru is clear and clean, but only
coming out in near drips and drizzles.
also, still curious about the WSM reference to a bleeding device connected to the slave bleeder and switched on???
just took off the flexible hose and pulsed the solenoid: same results??? drips and drizzles
since I am getting full blast pressure at the solenoid bleeder, can I assume that the solenoid is OK
and I must have a blockage either on the output side of the solenoid, or in the hard line from the solenoid
to the flexible hose??
I see an "Internet Myth" forming, here and would like some clarification/background.
This thread is the very first time I've heard anything about the PSD motors failing from overheating.....I've never seen this happen. As a matter of fact, I've never had to replace a PSD motor.
I get lots of vehicles in that have no fluid in the reservoir, can't build pressure, and have the PSD motor running continuously....and have had the motor running for weeks/months. There is nothing, in the PSD system, that will shut this motor off. There's no temperature switch. There's no circuit that tells the motor to shut off (if the system doesn't build pressure) after a certain period of time. There's no "level" switch in the reservoir. There's no protection, for the motor, anywhere. If the motor running continuously was an issue, it seems like Porsche would have built in a "safety" switch, of some sort.
I've repaired literally hundreds of PSD systems. Dozens of which have come in with the pump running continuously from loss of fluid. Never had a bad motor. Not a single one.
I'm just saying that if this was an issue, I'd be seeing dozens of burned out motors.....
I do agree that the motors get pretty warm and that seem too hot when you touch them (when they run continuously), I don't agree that they fail from running like this and getting hot.
Can you guys enlighten me?
I've got 3 or 4 PSD motors that have all melted internally (impressively so) with no other damage to the rest of the system. Brushes all have some lift left, but the motors got so hot internally that the windings have had their protective shield melted off.
anyone out there with comprehensive knowledge of the PSD and the hammer??
I am clearly on the back nine with this task, but need some additional help
in bleeding the slave, with the hammer, I am getting fluid in sync, with the pulses of the solenoid,
but I am not certain the fluid amount is sufficient??
I tested the flow directly from the hard line from the solenoid to the slave, eliminating the slave, pressure valve, and the
flexible hose, and the flow was the same???? (so that tells me the slave and pressure valve are good)
next, I took the hammer out of the equation, and energized the solenoid with a 12V power source. the flow was greater.
I am thinking the hammer actually modulates the pulse(s) at a lesser rate, creating a smaller volume????
can someone confirm that this is how the hammer works??
also, not clearly comprehending the PSD function. you can open the bleeder at the slave and no fluid is present, until the solenoid
allows flow. I would think that the whole process happens in milliseconds, and that fluid would be there at the ready, in high volume
and pressure. isn't that why there is 1800 psi at the accumulator??
Last edited by merchauser; 11-14-2018 at 08:35 AM.
I presume the hammer procedure replicates what happens in the working scenario.
The procedure Louie developed could not be easier to use. The accumulator as its name suggests accumulates pressure to the tune of 180 barg or whatever. The non hammer procedure simply initiates the solenoid valve with the slave bleed open and that allows fluid to pass from the accumulator into the slave and out of the bleeder.
When in use, the PSD system has a control algorithm and when the conditions measured create a demand, a specific amount of computed lock-up [range zero to 100%] is applied presumably controlled by the amount of pressure transferred to the diff actuator and this is released once the destabilising event is over. As you say the correction is applied in terms of milliseconds with the green light on the dash an advisory telling the driver the unit is trying to apply a correction.
Quite a sophisticated piece of kit and I suspect it has saved quite a few butts over the years never mind the poor thing the butts were sitting in! No idea why some folks do not seem to like the system and prefer the earlier LSD system but each to his own of course.
The procedure Louie developed could not be easier to use. The accumulator as its name suggests accumulates pressure to the tune of 180 barg or whatever. The non hammer procedure simply initiates the solenoid valve with the slave bleed open and that allows fluid to pass from the accumulator into the slave and out of the bleeder."
fred, to be clear, you are stated that when using the non hammer method, 1. the solenoid is energized the entire time, and not pulsed, and 2. the pressure and volume from the slave bleeder, should equal what is present at the solenoid bleeder?? is that correct?
fred, to be clear, you are stated that when using the non hammer method, 1. the solenoid is energized the entire time, and not pulsed, and 2. the pressure and volume from the slave bleeder, should equal what is present at the solenoid bleeder?? is that correct?
The solenoid is held open and the accumulator then discharges its charge into the slave cylinder which is open and thus the hydraulic fluid flows out directly with little in the way of pressure build up and will continue flowing until the accumulator is exhausted. If the bleed valve is closed and the system is liquid filled [i.e. non compressible] the pressure in the slave cylinder will quickly to come to equilibrium with that in the accumulator. Remember the accumulator is not just a volume it is what I presume to be a bladder and possibly a spring actuated piston to create the motive force necessary to quickly move liquid into the slave cylinder and hence effect the lock up.
The concept of pulsing is probably what happens to allow controlled increments of pressure to be applied until the computed amount of lock up is attained. Exactly how this is achieved I do not know but I suspect it will be either by applying a specific number of pulses to achieve a specific amount of fluid movement and thus the computed amount of lock up or there will be a feedback control loop wherein pressure is allowed in until the required pressure in the slave chamber is achieved. I suspect it will be the former approach hence the pulse concept.
I have not read the document Ake attached the other day but I suspect the methodology will be in there. Hopefully I might get chance to read it later this evening.
11-09-2018, 02:08 PM
