Power steering cut out

[stx133]

My E34 540 has developed a strange power steering issue, when accelerating heavily from idle, particularly if cornering at the same time (ie left or right turn from an intersection) the power steering "locks" for .5 secs and there is a "growl" from the left hand side of the engine bay.

all else seems to be normal. have taken it to my mechanic yesterday for evaluation, he was unsure and took it to a specialist of a look too, both were uncommitted as t owether the problem was the pump or the rack. have gone with flush out of the power steering fluid and research for now.

dont want to go $450 for a power steering pump rebuild if it is not the problem.

it there a pressure relief that could be going off on the step from idle to heave acceleration,
the power steering belt has just been replaced and is not making any noise, i do not believe that it is slipping

[shogun]

I read ast year on the German forum about such or similar case. Finally turned out that the engine mount was broken and that cause the engine to twist more, rsulting in too much bend of one hydraulic hose and blocking/reducing the flow of hydraulic fluid.

But is could be also as simple as a slipping belt.

[sal_park]

...or the rack...

If he thinks you've got a rack I suggest you find another mechanic.

sal

[stx133]

If he thinks you've got a rack I suggest you find another mechanic.

sal

my issue, power steering gearbox.

how does the servotronic system work. is this a potential culprit?

[genphreak]

Its big, its black and on a 540i I dare say it is very hard to replace ;)

I would buy a power steering pump rebuild kit ($20) and try that first. pskits.com or something like that. I think they are pretty much all the same (actually there are two, one ZF, one ? else) but you probaly have a ZF one. it is easy to remove and repair. Replace the fluid with synthetic- CHF11S if that is factory (always a metal reservoir) or synthetic trans fluid if it has the plastic reservoir (ie always factory spec CHF7.1 or Dexron). Some metal ones can use CHF7.1 and Dexron II (no matter what, it should say on all, though some use a sticker that may be able to one day come off).

If you need a new steering box, I'd advise checking the procedure to see you or your chosen repairer know what is involved and exactly what to budget. :)

[shogun]

no Sir, they do not have any kit for the M60 power steering pump, only ZF. That means for example the M30 engine. M60 engines have LuK or others. If you find a set for power steering pump for the M60 engine, let me know.

[genphreak]

no Sir, they do not have any kit for the M60 power steering pump, only ZF. That means for example the M30 engine. M60 engines have LuK or others. If you find a set for power steering pump for the M60 engine, let me know. Woot! Learned something new today, thank you Shogun!

It crossed my mind also though, the servotronic module could be bad, or even better the switching to it. I would try opening it up and checking the usual culprits; soldered joints with cracks or bad capacitors. If not that, and electrical still sounds feasible, check the RM and GM, or whatever the wiring diagram shows feeds it... as well as all the connectors for oxidation. It could just need some terminals cleaned up/replaced.

[stx133]

the cut out only happens under heave acceleraton from idle. if already moving no issues. i do not think the power steering pump could do this. even if rolling at an idle, the power steering works fine...

this is becoming a safety isssue. would love to have an idea of what to fix before throwing money at it.

Thanks

[Scott C]

I read ast year on the German forum about such or similar case. Finally turned out that the engine mount was broken and that cause the engine to twist more, rsulting in too much bend of one hydraulic hose and blocking/reducing the flow of hydraulic fluid.

But is could be also as simple as a slipping belt.

Stx133 - did you do the above?

[genphreak]

the cut out only happens under heave acceleraton from idle. if already moving no issues. Thanks

Check the reservoir filter (it is in the middle, you just open it up and remove the central nut. They are a sintered cylindrical tube about 1" in diameter and about 2" high on the plastic reservoirs, have never seen one in a metal one but its probably the similar).

You could check for signs of problems in the system by looking at that. An old one will usually soak dirt out into a rag if you roll it on one. If there are metal bits your answer may be obvious. I know that few people ever change the PS fluid (it is not under transmission level temperatures so probably last for years) but you could try swapping it out. A Dexron synthetic replacement could be used if you use that or CHF7.1, but your car is probably CHF11S in which case you will need to use that (available from BMW very easily). One 1L can should do you, be sure to drain as per the procedure. If you have LAD/Self leveling you will need more (2L).

Is this the case?

If you do, your problem is unlikely to be power steering related, but at least it will be eminently fixable :)

[sal_park]

Just a though - could the PS pump / system be fine - what about something physically locking up causing it to feel like the PS system is giving no assistance :

1) car accelerates from rest briskly
2) engine twists on mounting
3) PS pump hose is squashed by engine
4) PS assistance goes away
5) car has now got up to speed, drivers backs off throttle
6) engine moves back to normal position
7) PS hose is un-squashed
8) normal PS resumes.

[Ross]

I have a steering box from a '94 530, guess it's the same.
Shipping to Oz might be pricey. Oz, oh wait, same box for RHD???
Let me know if you need it.

[stx133]

Broken engine mount. U guys rock. :-)

[genphreak]

Hah! Well done.

You found the engine mount is bad, so it turns out to be a classic BMW fault:

1. Symptoms do not point to the root cause
2. Only occurs in a chain reaction of events
3. It is intermittent
4. Takes ages to troubleshoot
5. No normal mechanic can tell you why it might happen
6. once someone tells you the root cause, you remember you had heard of it before, somehwere.
... and the list goes on...

Good lukc fixing it. Search for old posts by mattyb , you need special spanners to get to it and it is best to modify one as he did. Also, you want the car up on a hoist to do it, if you haven't done so already.

ROFL

[stx133]

Hah! Well done.



Good lukc fixing it. Search for old posts by mattyb , you need special spanners to get to it and it is best to modify one as he did. Also, you want the car up on a hoist to do it, if you haven't done so already.

ROFL

Will have my mechanic attend to the work, i am an engineer and like to find root cause

[shogun]

come on, no big deal, did that on an Alpina B12 3 weeks ago and it took us just 2 hours. :D
But I have to admit, that was car number 4 or 5 within 2 months, all 750 V12 and we had a team of 4, and a pit and good tools including airtools. First one took us a "bit" longer :p

But you can also do it in the parking lot, see here especially in post 22 the pics
http://www.7-forum.com/forum/5/kein-tuv-109804.html

Also interesting to see how much smaller a engine mount gets over time, left pic bottom.
You might not be able to enlarge the pics without beeing registered there, better do that, lots of info on the German forum, I am member there since 2002

[stx133]

time and skin on my knuckles are of greater import to me at the moment.