2008 ML350 - Low Brake Pedal Issue

If you have to pump the brakes to get it to stop, do this check. With the engine running, but the car in Park, press the brake pedal down as you would normally and continue to hold pressure against it. if you feel it slowly sinking towards the floor there a high probability the master cylinder is going bad. If that is not what happens, suspect the brake booster is at fault.

I have a similar concern. I've replaced the sensor, booster and master cylinder and the car still feels like it doesn't want to stop. The front brakes are at 7 mil. Even though I press the pedal to the floor, it takes too long to come to a stop. Issue has been growing over the last 4 or so years. I have a 2003, ML 350 that is otherwise in perfect condition.

Check your rear brake and rotor. I never thought that was the issue until I replaced rear rotors.it fixed the problem.

Hello mamin123. Thank you for sharing. I had the rotors and front and back brakes replaced in 2015. Since then, I have only put 15K miles on the car. I will look into it.

When you brake if you feel vibration on right side of Driver Seat then it is Rear Brake or Rotors. Most likely it is rotors. If you feel left side of Driver seat, it is front brake/rotors. This diagnosis was by MB Dealer and it did fix my problem. Note: There is some extra play in ML350 brake is normal compare to other cars not sure why but it is.

Thank you. I haven't had any vibration when braking, just too much "play" as you called it. My mother has a 2015 ML 350 and it drives and brakes beautifully. I wonder if the problem was specific to the 2003 model.

You may not have noticeable vibration like me but if you deliberately check, while you brake you may see shaking on your left or right side of your driver seat. If it is left side, it is front brake or rotor and if it is on right side of shaking, it is rear side of brake/rotor. It may not be case for you but it is something you will have to deliberately look for. I had to take it to MB Dealer to find out.