Our 1988 W124 wagon is making an intermittent humming/droning noise ONLY when moving in the vertical plane.

That is, while driving over dips and mounds, the humming/droning occurs, but
immediately goes away.

It does NOT do this during turns or under acceleration.

A check of the front wheel bearings and pulling & rotating all wheels including shaking them hasn't shown anything.

Any ideas ?

Thanks,
:-) neil

1988 E36T AMG
1993 500
1995 E320T

Suspension? Sounds like a tire rubbing from your description.

Sounds like ball joints. Check fronts and the lower outer joints on the rear.

__________________
1986 300E (3/2002) Rear ended and totaled (10/2009)
2000 Xterra (5/2000)
1992 400E (11/2009) -Sold
1986 300E (12/2009) - Sold
2004 E500 Wagon (6/2013) - Sold

I had my tech lift her on the track and he found cracking flexdiscs and deteriorating diff mount bushings. We'll change these out later this week.

I'll tell him to check the front ball joints, and the rear outer joints, although we definitely hear it coming from the right front.

:-) neil

Flex discs changed, as well as the rubber mounts between on the exhaust-to-tranny mount up front.

Helped, but still no help.

I took apart the fan bearing bracket, seems to check-out OK, but the shock that's connected between the belt-tensioner and the engine block seems blown.

I'm going to replace it and let everyone know.

:-) neil

Replaced, but still there.

My indy and I are thinking exhaust since it only between 2800-3200 RPM when going over dips. . .

Any other ideas ?

:-( neil

Engine/transmission mounts or exhaust mounts.

__________________

Gone to the dark side

- Jeff

Your wagon has self leveling, yes, no? Check the oil level and other basics. How does she ride? Soft? Hard? (reverse cowgirl my fave). The sounds you hear may be hydraulic in nature.
Don (yeehaw)