pundit
07-28-2005, 04:01 AM
My '90 535i has non-servotronic power steering.
Recently, mainly at first start up on our cool winter mornings (5 degrees celsius) I began to notice the steering become very heavy when manouvering to exit my driveway. In fact after reversing and then moving foward slightly the power assist seemed to completely vanish to the point where I could not turn the wheel for about 2-3 secs. Then as I applied force to the wheel there was kind of a slight jolt as the assist came back and then off I would go. After that point it would never completely fail (once warmed up, until the next cold start) but the steering was generally heavier than normal.
Last night I drained and changed the fluid using Dexron III. Although there appears there maybe filter in the bottom of the reservoir, which I couldn't easily remove, there was no apparent restriction when blowing air through either the inlet or outlet (I know this is not a good filter test - air may pass easily while fluid may not!). Anyway, since changing the fluid, I haven't had the 'total momentary lockup' occur but the steering still feels slightly heavier than previous. I'm still a little suspicious of the filter however.
My other query is, while is the servotronic version (later 540's & M5's) has its level of power assistance determined electronically by road speed, the non-servotronic version is supposed to vary the assist based on engine RPM. As I cannot see any electronic control system to achieve this I assume this variable assist is built into the pump itself and must use some kind of hydraulic regulator to restrict hydraulic pressure as the RPM's increase? Yes? No? - TIA
Recently, mainly at first start up on our cool winter mornings (5 degrees celsius) I began to notice the steering become very heavy when manouvering to exit my driveway. In fact after reversing and then moving foward slightly the power assist seemed to completely vanish to the point where I could not turn the wheel for about 2-3 secs. Then as I applied force to the wheel there was kind of a slight jolt as the assist came back and then off I would go. After that point it would never completely fail (once warmed up, until the next cold start) but the steering was generally heavier than normal.
Last night I drained and changed the fluid using Dexron III. Although there appears there maybe filter in the bottom of the reservoir, which I couldn't easily remove, there was no apparent restriction when blowing air through either the inlet or outlet (I know this is not a good filter test - air may pass easily while fluid may not!). Anyway, since changing the fluid, I haven't had the 'total momentary lockup' occur but the steering still feels slightly heavier than previous. I'm still a little suspicious of the filter however.
My other query is, while is the servotronic version (later 540's & M5's) has its level of power assistance determined electronically by road speed, the non-servotronic version is supposed to vary the assist based on engine RPM. As I cannot see any electronic control system to achieve this I assume this variable assist is built into the pump itself and must use some kind of hydraulic regulator to restrict hydraulic pressure as the RPM's increase? Yes? No? - TIA