Self Levelling Suspension Noise - The Unofficial BMW M5 Messageboard (m5board.com)

Graeme Hancock · 24th June 2008, 06:19

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 ?

Regards

Graeme Hancock,
Gold Coast,
Australia

nebpor · 24th June 2008, 14:49

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!

EDC Removal: Done!
Removing EDC, couple of questions
sls replacement
Anyone deleted rear SLS with Koni / Dinan springs? Need help!

Graeme Hancock · 25th June 2008, 03:54

Thanks nebpor. It's interesting reading but there seems an equal feeling that you should retain the SLS.

So to my other question: what is causing the resonance in the lines that sounds like a croaking frog and how do I get rid of it ?

Graeme Hancock · 21st August 2008, 09:18

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.

Graeme Hancock

davidoli · 21st August 2008, 09:28

Congratulations and thanks for the positive update !

farrell · 21st August 2008, 10:58

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.

Farrell