funny noise s500 underbonnet w221

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jonnyboy

MB Enthusiast
Joined
Nov 27, 2005
Messages
2,564
Location
Camberley, Surrey
Car
1991 sl300-24 project,s124 280,w115 no interior, w108 project no engine
Esteemed gents.
Acquaintance arrived today. Caught me unawares.
9 yr old w221 with 30k miles, owned from new.
Against my advice, its going in to main dealer for a service.
"funny noise - can hear inside and out".
Expecting the worst I got him to pop the bonnet.
Narrowed down the noise to emanating from under a black cover at rear o/side of the engine bay. Noise still there with engine off, ignition on.
Best I can describe it is like dry bearings on a motor/electric fan, or like a noisy hard drive!!! I did once have a car with a noisy heater fan that sounded like it, and was as intermittent.
Stuck a vid on photobucket, you might need to turn the sound up to hear over Mr Noisy walking on my gravel while I filmed....:-
http://vid61.photobucket.com/albums/h55/entire54321/MOV_0427_zps3vlw7p65.mp4
I couldn't investigate more as only got one working arm at the mo !!!!!

Any thoughts? Thanks
 
There used to be a fan that cooled the ecu, think this was on the w220, worth a try. But it does seem a bit noisy for that. Also if I remember rightly when the fan failed it would trip a low coolant warning or some other weird fault not connected with the problem.
 
Ps. the heater fan on other side and under dashboard so you can discount that one
 
Definitely not a fan cooled engine ECU as this car had its ECU fail last year - apparently its on top of the engine and gets too hot. £2k bill that was...
I wish I'd tried to left-hand remove that cover.
 
anyone any other ideas?
 
Gents

Main dealer couldn't hear it when they did the service apparently, even though noise was worse upon collection than when it was dropped off......

It's been intoday, technician agreed he could hear something, insists the noise is behind the osf wheelarch liner:-

"theres loads of stuff behind there - I need to strip off the wheel archliner and connect the diagnostic to pinpoint" - I'm not sure how stripping the liner off to connect the Star helps, but that's just me....


Anyone have any ideas at all as to what could make that noise behind the osf liner? Happens with ignition on and engine off, or running. Vid linked above
 
It could be anything. Remove the wheel arch liner firstly and have a look about.
 

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