Bad ABS Motor?

Sam Adams • 7 October 2019
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Hey all, Came across an article from your site on repairing a ABS unit on a Mercedes.  

 

My Mother came to my place today wanting me to look at her car, A C230.  She said it was making a loud humming sound and would go away when she applied the brakes.

I took a look and when the key was on or engine started there was a loud hum. Sounded like it was coming from the rear of the car, I popped the trunk and could hear it back there sounding like it was coming from the rear wheel driver side.

After further inspection I found that the Motor on the ABS unit under the hood is where the noise was coming from, At least I think it is the motor or something the motor is spinning.

 

I want to repair it for her myself if at all possible rather than buying a new unit.  I have uploaded a video of the motor making the noise with and without brakes applied.    It gets quieter with brake pressure.  I found it odd that the sound travels down the car to the driver side rear wheel pretty loudly but not the other wheels.  Could this mean the issue is not the motor but something else in the unit?

I have uploaded a video of the motor hum with and without braking with engine off here... https://www.youtube.com/watch?v=rh5Y95zdNMg with some info in the video description.  I would like to maybe take the motor apart and fix it myself if possible, new bearing if hopefully, that is the issue with the humming or whatever.   The issue with the motor always on is the fix you guys had up I was looking at.  I am thinking maybe it has been running ON all the time for so long and no one knew it that now the motor is wearing out. She told me the BAS ABS light has been on for a long time, like a year.  Brakes work fine but I would like her ABS to work properly as she has a lead foot. 

If yall could take a look/listen to the video and share any advice, ideas or anything else I should look at or test to share more info that would be greatly appreciated.

For now, I have disconnected power to the motor.     

Thank you for any advice.