W124 "Whaaa" sound during acceleration
 

I noticed yesterday my 1987 260E is making a "whaaaa" sound during acceleration. The sound is similar to middle C on a piano and increases in volume with speed, but then it goes away once the car is at a steady speed. I revved the engine in the parking lot and I was not able to reproduce the sound. It has 213K on the engine/transmission, but still runs very well and sounds acceptable. The sound seems to be coming from the passenger side of the car. Is this likely to be wheel bearings?

New parts:

• Front inner/outer tie rods on left and right sides
• Front struts
• Strut bump stops and boots
• Strut mounts
• Front sway bar bushings
• Rear shocks
• Shock bump stops and boots
• Rear LCAs

You said louder as you go faster, but does it change with shifts?

I had this with mine, but it was because I removed the ABS sensor. Upon reinstall it shifted too far forward and was riding on the pick-up ring! Glad I drove it just around the block. Thought it was the bearings since it was consistent with speed.

Usually if bearing are making the noise it will go away as you turn one direction and get louder turning the other way. Although driving with bad bearings is... well bad.

This might be dumb but I had my car making a noise that I would describe as a "whaaaa" sound and it ended up being my fan clutch pulley giving out allowing the fan to hit the pulleys on the driver side. Check your fan clutch clearance to your pulleys and see if there is any play. It would only happen when I stepped on it causing the fan to flex back just enough, and with bearing giving out, allowed it to rub.

My 92 SL does this
 

I've always chalked it up to driveline. Seems to happen more in 3rd, under load. Diff?

Could be. But keep in mind, its a Mercedes-Benz! It should not be making weird sounds. If it is, there is something wrong. Could be minor and never been an issue or it could be something about to fail.

So I take every noise seriously until I know what is making it. Then I decide if it needs to be fixed now or can wait for a later day and make it part of a larger project.

Good ideas. I will pay attention during the ride home tonight and look at the pulley. Thanks, Bob.

I noticed the sound occurs when the engine rpm is between 1300 and 1600. The noise does not appear when the engine is idling or at other rpms. Additionally, I do not notice the noise when I am turning without pushing on the throttle. I have not checked the pulley yet.

Well now I am confused. Certain RPM and not there when turning. Really no clue on this one.

Could it be something like a heat shield that may deflect a little when the body twists in a turn? Im outta ideas.

Sounds like bearings, no? More stress on them when turning, more stress when accelerating. 1300-1600 is low rpm, low-speed = more dead weight to get moving/more stress. A cheap and necessary repair even if that's not the cause of the noise

Maybe. But I never had bad bearings make noise relative to RPM. They were always constant, unless turning. Turn slightly on a straight road one way and they get louder, the other way quieter. Maybe the geometry of the Benz is a little different.

Well on one like this, you've got to get creative. and if you're going to throw parts at it, if you've done all those expensive suspension parts, why not do the bearings too?

I had a shimmy that 2 techs and several people on this board told me was most certainly not bearings. I even had a tech tell me the bearings don't need to be replaced.

Guess what? It was the bearings. And this was a 400E. They should be a maint item - every 10 years/100k.

Informative ,and surprised it was the bearings !

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I noticed the noise has shifted to 2000 rpm, but it still does not seem to be steering related. I really hope it is not the bearings.

Just went through a front right wheel bearing...would you believe it, only a short time after having them all repacked.

My sound was like I had snow tires on the car - just above the typical road noise and dependent on road speed. Couldn't really hear it below a certain speed.

Compared to suspension work (just did all four shocks and all of the hardware), wheel bearings are dirt cheap...

How hard was it to change the wheel bearings? Do I need any special tools for the front or rear wheels?