Odd power steering failure - The Unofficial BMW M5 Messageboard (m5board.com)

mottati · 4th November 2003, 18:51

Hello gang,
I was at the bmw cca golden gate chapter drivers school this past weekend at sears point (aka infineon). First time with the M5, what a great car on the track, had a blast.

On day 2, on my second run, i was signed off, driving alone, enjoying myself. I was thinking "wow, the steering feels really good this run" until my cool down lap, when i realized steering effort was quite high. Pulling into the pits, i noticed i had no steering assist, to the Left only. (normal to the right). Didn't matter if sport was on or off. I checked the fluid, to find some had spewed out thru the breather on the strut tower area, but the level was still within the normal range. I spoke with a couple of people, one who suggested pulling the fuse to the servotronic, to see if it was blown. It was fine, and after reinstalling the fuse, no change. Someone else suggested somethin amiss the steering box, but i should be ok to continue my day. The car drove just fine on track (could argue better steering feel than normal) with no assist to the left. Drove home that night and a couple small runs the next day, no change. THe next day, all is back to normal!?!
Any ideas?
Mike

Teutonaddict · 5th November 2003, 01:44

Mike-

I had an odd power steering experience that had an unusual root cause, although it was somewhat dissimilar from yours. I'll share it anyways in the hopes that it may get your SA thinking about the whole range of possible solutions.

And FWIW, I push fluid out of the filler cap each time I track my Beast. In fact, they overfilled after my Inspection-II (60K miles) that immediately preceeded a weekend at Mid-Ohio. It leaked fluid through the fender liners, and onto my track tires(!!). Siphoning off the excess and wrapping the box in paper towels prevented further disaster.

I had an intermittent PS problem that was caused by an unfortunate routing of the power cables to the PS motor. Apparently, under chassis flex (track cornering and freeway cloverleafs) the cable would get pinched between the PS unit and the S62 engine block, and short out. It would then re-set upon a cycling of the ignition.

The symptoms were a sensation of change in boost in the midst of a corner. There would be a slight surge, and then no boost at all. They replaced several PS components before realizing that the circuit was being shorted out during hard cornering.

I realize that does not explain your one-direction-only issue, but I thought I'd add some more fuel to the fire. Good luck, and let us know what you learn!

-Dave

mottati · 5th November 2003, 02:14

Huh, that's interesting. I'm gonna hold off on going into the dealership. I can just see the looks

when i tell them i lost boost only in one direction. The tech would likely get in my car, start it, turn the steering wheel and report "could not duplicate condition, customer is a dumb_ss" since it's all working fine now. I imagine it'll recur, and i'll get it in while it's in it's odd mode. I'm thinking about making a little overflow catch for the vent hole in the ps cap. My 528 would "vent" a little fluid, but this is a bit more messy in the M5. I saw a guy with a 540 who used drip irrigation pieces (no kidding), which seem to fit perfect into the vent hole in the P/S res. cap. He made a little loop, i may try to find a little container to hold the overflow.
Thanks for the input on your p/s problem, i'll keep it in mind.
Mike

Teutonaddict · 5th November 2003, 19:19

Quote:

Originally posted by mottati
I can just see the looks when i tell them i lost boost only in one direction. The tech would likely get in my car, start it, turn the steering wheel and report "could not duplicate condition, customer is a dumb_ss" since it's all working fine now.

Now that you mention it, finding the ultimate solution did require a ride-along with the dealership's M-Technician. Since it only happened during aggressive cornering, the dealership was uncomfortable sending the tech out alone to try to replicate the conditions. They called me and asked me to drive the car to try to trigger the condition. After I did that, I turned the keys over to the tech so he could do the same. Only then did we find out what was really happening.

Granted, most $tealerships would not take the time or expend the effort required to figure this out. My SA happened to be the Chief Instructor for our local CCA chapter, so he would exert his influence in getting the Tech's to take my descriptions seriously.

Let us know what you learn!
-Dave

DavidS · 6th November 2003, 12:48

Dave,

Very interesting to hear of that fault.

Would you like to take a picture and point out where the cable got shorted, please? (or simply indicate graphically on an existing picture of the engine bay)

Best Regs,

David

louv · 7th November 2003, 02:58

Quote:

Originally posted by mottati
... My 528 would "vent" a little fluid, but this is a bit more messy in the M5. I saw a guy with a 540 who used drip irrigation pieces (no kidding), which seem to fit perfect into the vent hole in the P/S res. cap. He made a little loop...

Mike,
Yeah I used to have that same problem (vented fluid) at the track. I saw the 540 driver's mod and added it to my engine.
The two pieces are: 1) a straight-line drip irrigation connector, with one end shaved to fit, and 2) 12" of Aquarium air hose. Both "parts" were available at the Wal-Mart just down the road from ThunderHill Racetrack!

As for the Power Steering "failure", I had that problem once. Exited off the freeway, turned onto a surface street and almost didn't make the corner because I had absolutely no steering boost. It lasted for about 2 blocks, then fixed itself. Since I had just been driving back from the dealer, who had just fixed a leak of power steering fluid, I called them up and demanded that they come and fix the car. I was cranky. Neither they nor I could ever reproduce the problem. It never came back.

Teutonaddict · 7th November 2003, 18:24

Quote:

Originally posted by DavidS
Would you like to take a picture and point out where the cable got shorted, please? (or simply indicate graphically on an existing picture of the engine bay)

David-

I have no earthly idea where this all took place. I relied exclusively on the verbal descriptions of my SA and his Tech. It made perfect sense to me, and I did not see fit to pursue it further.

-Dave

DavidS · 8th November 2003, 00:46

Dave,

If you should get the opportunity sometime to ask your SA where it was, it would be great, because I actually have no idea as to how much the engine moves about in the engine bay when accelerating, braking and cornering to the max, and how much clearance is needed for the cables.

Best Regs,

David