intermitent hum through steering column
 

W124 400e 62K (already had my 60K service) - I've been having this intermitent hum though my steering column. It seems like it could be the powersteering pump or the water pump. It was happening only when I'd make right turns from a stop and even at that it was only occasionally. Then I noticed it would happen after a long stint on the hwy, once I'd pull off and had to stop. Then as I would pull away I'd hear/feel the hum. It went away for almost a month, but today on my way home, I heard it again just a couple miles after getting off the fwy. My belt tensioner and power steering pump have been replaced within the last year/10K -

Any input? Am I on the verge of yet another $$$$ repair?

This may not be too much help, but I know the W124 power steering system will "hum" through the steering wheel when its low on fluid. This happens routinely to me because I have a really slow fluid leak. So, when it gets low I get that familiar vibration when turning. But typically it doesn't matter the direction being turned.

As a relatively inexpensive thing, first, you could check the fluid level. The owner's manual should show you the fill line indicator.

Second, you could try changing the power steering filter. This may be effective - especially if you put on a used pump. The power steering filter is held in by that center post in the fluid reservoir. It's a doughnut shaped thing in the bottom of the reservoir tank.

Do you happen to know what kind of fluid you are running in the system? I like the newer power steering fluid that is more like a hydraulic fluid (its clear) than transmission fluid (red). Havolene Power Steering Fluid.

Ken300D

Thanks for the input, I'll check it out. I did replace my pump with a rebuilt and it has started to leak (really slight). My mechanic (Enrique/Mr MB Motors) tells me that this is a common occurance among W124s. I'm assuming he checked the fluid level because he is really thorough. But I'll check anyway.

I'm pretty sure the humming is caused by air bubbles when the fluid level gets low. I have to top off my reservoir about once every two months, and it only takes maybe four ounces of fluid to do that.

Ken300D