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Power Steering Failure - Then back to Normal

17K views 10 replies 6 participants last post by  mattml430 
#1 ·
Hey guess. Today while driving i experienced a sudden power steering failure while driving. No lights came on and upon a new ignition cycle everything was back to normal?!

what can cause a sudden power steering failure that last only for one cycle? it is odd because now the system seems to function normal again. There was no whine or abnormal noise during the failure.

Reservoir was changed only about 2 weeks ago with proper bleeding procedure because i experienced the infamous whine. I can not see any leaks and fluid level appears to be normal about 10 mm below opening in reservoir.

thx for any help - phil
 
#2 ·
You are an ML vet and you know these problems don't just fix themselves. However the ML does have a lot of 'sudden' glitches that are usually electronics related - they tend to disappear with a simple restart, just like rebooting the system. I'd advice to keep driving and monitor to see if the problem reoccurs. Then make a decision depending on whatever data you have collected.
 
#3 ·
Air bubble in the line? I read you did the proper bleed. Only thing I can think of short of the belt slipping.
 
#4 ·
Yeah i was thinking of electronics as well. However i dont know the set up of the PS in the ML. I do not think they are any eletronical clutches or control valves in there... i might have to see if alldata has some scematics.

Hmm air bubble and belt slipping are both possible. BUT why would the air bubble dissappear almost immediately upon restart?...

for the belt: yeah maybe when it shut down and stopped it got grip again.. haha to be all geeky "the coefficient of static friction is higher than the coefficient of kinetic friction" hehe...and upon restart it had enough grip to turn over the pump and keep going.

i will observe behaviour and report back if it reappears. Unfortunately I absolutely agree with darkmen," these things usually just dont fix themselves" in fact i think they are often the forerunners of some expensive repairs.

thx guys (or guess as my dictionary corrected it).. ;)
 
#5 ·
Hmm air bubble and belt slipping are both possible. BUT why would the air bubble dissappear almost immediately upon restart?...
Can't answer this, but I had it happen a LONG time ago on a Camaro. Lost power steering and I immediately flushed it/bled it to get it to come back. Never an issue after that. I still have no clue how the air got in there to begin with since it was stock/never touched.
 
#6 · (Edited)
Hello sgtpepperaut!

Long time buddy!

I'm sorry to be the bearer of possible bad news but this is sounding like the problem I used to have with my ML55; which as you know has speed sensitive power steering.

The system is meant to work by stiffening up the steering to aid in vehicle stability at speed.

When it goes faulty, it stiffens up the steering even at low speeds; resulting in a heavy steering.

The speed sensitive steering is controlled by the traction control module so if you have problems it is all pointing towards the module; which unfortunately costs $$$ to replace and needs coding by dealer afterwards.
 
#7 ·
Hello sgtpepperaut!


The speed sensitive steering is controlled by the traction control module so if you have problems it is all pointing towards the module; which unfortunately costs $$$ to replace and needs coding by dealer afterwards.

HMMPF!!! ohh no. i had my ETC/BAS light come one a couple of days ago. it stayed on for two cycles then dissappeared. THX i feel that is the root of my problem.

On the other hand i never really felt the PS stiffening up much...even hat higher speeds. (even when i got the car) ... the only reference i have however is my friends BWM Z4 that at higher speeds makes the wheel incredible hard to turn. Its almost a "reverse power steering"...

hmm how much is the TCM?

and edit: Good to see you are still alive buddy :)
 
#9 ·
very informative thread! thank you.....

now instead of seeing two possible problems i see ten. :D

FAR...did you ever have the ESP/BAS light illuminate?

i had the warning lights come on like once or twice a year. I am not sure i can trace that behaviour back to driving through water at higher speeds...but is possible.

Given that everything works fine again i tend to see the TCM as the culprit. Maybe some worn brake linings or even a problem with the brake light switch triggered a fault in the TCM which consecutively disabled the SPS.

I am not sure what action to take at this point other than to wait for the problem to reappear. Maybe ill measure the solenoid resistance but i dont expect any problems with it.

thx for help guys.
 
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