I last asked this question 8 years ago when the great M5 guru, Christian Wagner, graced the forum pages.
After a blew a steering hose and had it replaced, the car had a noise like a croaking frog that we traced to the self levelling suspension lines.
All the hoses connected to the steering pump have been replaced again, the SLS valve actuator has been replaced, the bar on the device has been 'locked' up, the system has been bled many times but the noise remains.
Christian said the easy fix was to remove the SLS and replace with 'conventional' shocks. If I did that, what shocks are preferred ?
Would I also need to replace the springs ? Can I just block off the line from the steering pump ?
Altenatively, does someone else know what the fix for the problem is ?
Hi Graeme, there are a few details threads (with the all important pictures!) on here from recently about completely removing the SLS system and the options open to you for suspension, so I'll point you at one of them to get you started!
Thanks to a couple of members who PM'd me to help the search.
In case anyone else suffers from a pulsing noise in the SLS lines after changing one of the power steering hoses, here's what was discovered.
There are at least 4 possible causes and in my case, it was narrowed to:
there are 2 restrictors in the OEM style hose;
there is a gauze basket clipped into the hose end that fits to the pump;
the exit hole for the SLS line on the pump is only about 1mm diameter;
there is very stiff braiding surrounding the end of the hose.
My service manager removed the gauze basket and the 2 restrictors from the rigid hose and used a non braided hose. Then he drilled the exit hole out to 1 eighth of an inch.
Problem solved after years of frustration and more than $2,000 in replacing this, that and the other.
Cheers Graham
Thanks for the pm.
Another car in UK has turned up with symptoms similar to yours.
Just waiting to see if noise re-occurs but defintely down to flow restriction.
Some restriction is reqd to modulate pressure & tune out noise, but blockages
are not welcome.
I TOO have this vibration noise coming from SLS. i looked through the links posted above but i dont see any help from them. I may be blind and dumb. my SLS vibrates like crazy. drives me nuts. Ill keep this updated if i can find out how to shut it up. buying more power steering fluid might work. or messing with the SLS actuator thing by the Diff.-92 M5
With all due respect, the answers are indeed probably in the preceding posts.
Unfortunately though, it is a trial and error process and I can only recount my own experience, albeit, I did go well beyond BMW techs to at least confirm that the problem I had was due to fluid flow and or flow restriction and or a 'cavitation' type issue principally emanating from the pump.
After getting the car on a hoist and establishing for myself and 2 mechanics that the noise was in the SLS lines towards the rear axle region, (as one BMW service centre suggested it was the gearbox) I went looking for the possible causes. To 'help', I at least knew the problem did not exist before I blew a steering hose. Replacing the hoses with OEM items then custom made up hoses did nothing. Replacing the rear actuator based on the 'logic' that if it had been starved of fluid in the blown hose event, it may not be working properly didn't do anything either.
I forget now what else I did except that I consulted a hydrauilc engineeer who confirmed that the noise was coming from the SLS and must be due to pump and or flow restriction issues in the hoses.
After chasing up some more dry gullies, my new mechanic told me another dealer centre had solved a similar issue by removing the restrictors from the hoses on the steering pump and that he himself had solved another one by drilling a larger hole in the pump outlet.
On my car, as stated in my previous post, the mechanic implemented both options and drilled a larger hole plus removed the restrictors from the hoses.
I suggest that you might follow the process I did and in order:
1. Get the car on a hoist and satisfy yourself that the noise is in the SLS;
2. Prove that the system is self bleeding and that it is not the valve actuator;
3. Remove one restrictor at a time from the hoses;
4. Drill a larger hole in the pump.
Please bear in mind Farrell's caution though: the restrictors are there to control flow and so one at a time is preferable to a carte blanche approach.
Before that though, are you able to tell us if the problem started after an event like a blown hose or it just happened at random ?
Thanks Graeme for your help. the noise was present when I bought the car. Previous owner said it was exhaust vibration. It seems like there are a few new hoses from steering pump (will comferm tomorrow). I think the noise comes from the back Thought it was just the rear valve so yesterday I took apart the rear valve arm that is connected to rear sway bar. made the sound louder + goes to higher rpm. So tomorrow I'm taking it to a good German friend mechanic...
Hi Graeme, there are a few details threads (with the all important pictures!) on here from recently about completely removing the SLS system and the options open to you for suspension, so I'll point you at one of them to get you started!
.. as an aside, its replies like these that make me love the M5board more than any other. On most other boards, the response to Graeme Hancocks post would be "use the search function". Im sure we can all agree that thoughtful respones like nebpor's, especially for us newbies, are very much appreciated.
4Likes
Thought it was just the rear valve so yesterday I took apart the rear valve arm that is connected to rear sway bar. made the sound louder + goes to higher rpm. So tomorrow I'm taking it to a good German friend mechanic...
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