PSD fluid level way above max
11-10-2023, 02:29 PM
#1
Pro
Thread Starter
PSD fluid level way above max
I found this situation while doing some undercarriage houskeeping. No errors or problems with PSD. Is the level measured with engine off like this? Should I just let it be, or should I remove some fluid?
11-10-2023, 03:11 PM
#2
Rennlist Member
Remove liquid to the Max level. It is measured like this, no need to run the engine. Even if you leave it like this, nothing will happen, you are riving around with this for a long time already...
11-10-2023, 05:10 PM
#3
Team Owner
Based on the color , it might be wise to change the brake fluid in the PSD system though,
I would Use ATE brake fluid
I would Use ATE brake fluid
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Schocki (11-11-2023)
11-11-2023, 05:46 PM
#4
Pro
Thread Starter
Thanks, yes, probably a good idea to flush the system when I already have the fender liner out. Don't know when it was last done. I found this so I guess it shouldn't be too hard. http://www.928intl.com/repair/psd1.pdf
11-12-2023, 01:20 PM
#5
Rennlist Member
So if the car has been sitting for a while then it is very likely that the fluid in the accumulator has returned past the check valve back into the reservoir, raising the level above "max".
Here are the instructions for checking the level, from the PDF referenced above:
33. Connect the hydraulic pump motor connector and metal retainer clip. The pump will start and fill
accumulator. When the motor stops fill the reservoir to the maximum level line and replace the
reservoir cap.
accumulator. When the motor stops fill the reservoir to the maximum level line and replace the
reservoir cap.
Cheers,
11-12-2023, 04:49 PM
#6
Pro
Thread Starter
The PSD system can't create fluid, but there is another place where fluid is stored: In the pressure accumulator (the large yellowish "can" in your photo). It's a simple system: Atmospheric reservoir, pump, accumulator, and pressure switch. The accumulator is a high-pressure vessel with a diaphragm that can store fluid at 1000 psi (or whatever pressure the system runs at). Whenever the key is on, and the pressure is low, the pressure switch activates the pump to build pressure and "charge" the accumulator. It is the pressurized fluid in the accumulator that activates the slave cylinder on the differential.
So if the car has been sitting for a while then it is very likely that the fluid in the accumulator has returned past the check valve back into the reservoir, raising the level above "max".
Here are the instructions for checking the level, from the PDF referenced above:
So certainly change the fluid and fill per the above. Generally, whenever you first turn the key on after the car has been sitting for a while, you should hear the pump running for a few seconds to build pressure. If it doesn't build pressure then you will get a warning on the dash. And if the pump keeps cycling on-off with key on (engine on or off) then the check valve is not holding pressure-- but flush the fluid before worrying about that.
Cheers,
So if the car has been sitting for a while then it is very likely that the fluid in the accumulator has returned past the check valve back into the reservoir, raising the level above "max".
Here are the instructions for checking the level, from the PDF referenced above:
So certainly change the fluid and fill per the above. Generally, whenever you first turn the key on after the car has been sitting for a while, you should hear the pump running for a few seconds to build pressure. If it doesn't build pressure then you will get a warning on the dash. And if the pump keeps cycling on-off with key on (engine on or off) then the check valve is not holding pressure-- but flush the fluid before worrying about that.
Cheers,
