Quote:
Originally Posted by o2bad455
SYMPTOMS: We just encountered the same loss of steering assist (as here: https://xoutpost.com/bmw-sav-forums/...-suddenly.html) without any warnings or other symptoms on our '08 E83 X3 N52 M-Sport (USA Spec). The power steering (PS) simply stopped assisting after stopping for gas on the way into a congested city, which almost made us overshoot an exit ramp and then made tight curb-side parking unexpectedly challenging. There is no noticeable fluid movement in the reservoir with the engine running, but the belt's good, pulley's not wobbling, no noises or PS leaks.
CONTROLLER?: I thought it might be a steering controller fuse, but fuses 66 and 69 both seem to be fine. Is there any possibility that this could be a controller issue? If I understand correctly, although it seems not to be well documented, the steering controller supposedly actively adjusts the amount of assist. Anyone know if it adjusts to zero assist under any circumstances, even if just in a failure mode? I couldn't find any relevant fault codes using INPA, but just got ISTA working again (under an updated VBox Win10 VM, FWIW) and it just reported code "0000A1", description "MRS: No message from DSC control unit or message incorrect", and mileage "-1". Could that code be relevant? The only two other codes (for gearbox oil wear and a number-plate light) both showed actual mileages.
RESERVOIR?: I read that the PS reservoir has a non-removable filter. If it got plugged somehow, could that cause the issue? Has anyone successfully removed the internal reservior filter (I'd add an external one, of course)?
PUMP?: If not the controller or reservoir filter, I guess we'll be ordering a new PS pump. But I've truly never had a hydraulic PS failure anything like this before. It makes me wonder: Are these PS pumps' impellers made of plastic? If so, is there a metal impeller version or upgrade available? Our vehicle assembly date per the door-jamb VIN sticker is January 2008, although ISTA just identiifed it as September 2007 (I presume retrieved from a control unit, but no idea which). It looks like there were several different pump versions in a 2-3 year period, so I guess I ought to at least pull the lower shield off to take a picture before ordering.
FLUID?: I will say that the fluid had been right at the min mark when cold and about halfway to max mark when hot since we got the X3 a couple of years ago. When on a long trip this past summer, I decided to top it off to full when hot using Prestone European Power Steering Fluid, which listed "BMW" on the front label and "CHF-11S" in the fine print. After pump replacement, exactly which readily available fluids should we use or avoid? |
Alright...cool. Lets see if we can narrow down your issue here. I highly doubt adding in different hydraulic fluid would absolutely kill something.
Do you know how to use mdecoder? Can you check on your vin if you have option code "216" assigned? This will tell us if you have servotronic steering.
You might already know this but, here's what NEWTIS says:
New: In E83 the Servotronic is integrated in its own control unit.
The Servotronic is available as special equipment (option 216).
Brief description of components
The following control units are involved in the Servotronic:
Servotronic control unit (SVT)
The SVT control unit specifies the nominal values for controlling the Servotronic valve (hydraulic pressure). The SVT control unit is connected to the PT-CAN (powertrain CAN) and K-Bus (body bus).
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DSC control unit (Dynamic Stability Control)
The DSC control unit delivers the car's road speed signal. The DSC control unit and SVT control unit are connected by the PT-CAN.
DME or DDE (Digital Engine Electronics or Digital Diesel Electronics DDE)
The Servotronic receives the signal of whether the engine is running from the DME or DDE over the PT-CAN. The Servotronic only activates the Servotronic valve when the engine is running.
Instrument cluster (KOMBI)
The instrument cluster delivers the terminal status (e.g. terminal 15 ON) and the kilometer reading.
If you indeed have the option on your car, the module needs to be on PTCAN in order to determine road speed to adjust the valve. This would make sense if your DSC is not "on" for some reason.
Do you have the "trifecta" lights on your dash? 4x4, amber-BRAKE, etc....?
This might be the case if the MRS module is complaining about not seeing the DSC.
Here's some miscellaneous info:
SBT Enclosure E83 General information on Servotronic, En
Important. Do not hold the steering wheel at the limit stop for a long time.
The power-steering pump does not have a limit stop mechanism. The power-steering pump may become damaged if the steering wheel is held at the limit stop for a long time (1 minute and longer).
Note: different power-steering pump for different engine variants
Different power-steering pumps are used for different engine variants. For petrol engines the equalizing tank is installed separately from the power-steering pump. For diesel engines the equalizing tank is flange-mounted on the power-steering pump.
Note: cooling fins instead of cooling coil
For diesel engines the power-steering cooler has cooling fins instead of only one cooling coil (introduction also planned for petrol engines).