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Red 1987 560SL, Silver 2002 ML320, Grey 2010 ML350 (gas)
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Discussion Starter #1
Normally, I do my own brake jobs - pads and rotors. Two years ago I replaced the front and rear pads on my 2002 ML320 (now, with 170k miles). Afterwards, I noticed the brake pedal was soft. It would stop the ML with no problem, but now the pedal would almost go to the floor. I check the brake fluid level and even bled the brakes, but the pedal was the same. Again, the ML would stop easily, but the pedal would be "soft" or "lots of pedal", but stop the ML safely.

Fast forward to today - I put the ML in shop with my local MB mechanic (not a dealer mechanic) to have new pads and rotors. When he took if for a tesk drive and felt the soft pedal, he called me and told me that the Master Cylinder needed replacing.

He replaced the Master Cylinder and the soft pedal persists. So, he called me and said it needed a Brake Booster.

He replaced the Brake Booster and the soft pedal persists.

I just got off the phone with him and he says he doesn't know what is wrong with the brakes or brake pedal but is going to troubleshoot some more.

Anybody have any ideas on what might be causing so much play in the Brake Pedal? Any advice "In General"? Thanks!

-Brian
 

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Red 1987 560SL, Silver 2002 ML320, Grey 2010 ML350 (gas)
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Discussion Starter #2
Anybody have any ideas on what might be causing so much play in the Brake Pedal? Any advice "In General"? Thanks!

-Brian

Oh, I asked him if he had bled the brakes and he said, "Yes".
 

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w163 02 ML500 W210 97 E50Amg w202 99 C230K w124 - need more space, time to build again
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Dallas, Texas
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Two years ago I replaced the front and rear pads on my 2002 ML320 (now, with 170k miles). Afterwards, I noticed the brake pedal was soft. It would stop the ML with no problem, but now the pedal would almost go to the floor. I check the brake fluid level and even bled the brakes, but the pedal was the same. Again, the ML would stop easily, but the pedal would be "soft" or "lots of pedal", but stop the ML safely.
So, by your own admission brake pedal feel/travel is somewhat different then most. Vehicle stops on a dime with pedal 3 inches from the floor. Yes, you can push it further but why would you?
 

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Red 1987 560SL, Silver 2002 ML320, Grey 2010 ML350 (gas)
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Discussion Starter #6
So, by your own admission brake pedal feel/travel is somewhat different then most. Vehicle stops on a dime with pedal 3 inches from the floor. Yes, you can push it further but why would you?
After I replaced the pads two years ago, I did not have any problem stopping the ML. The pedal had a lot of "play" but there wasn't any problem stopping. Over time, I found myself automatically pumping the pedal, which shortened the play of the pedal.

My wife drove the ML once and refused to drive it any more with the pedal having so much play.

=Brian
 

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Red 1987 560SL, Silver 2002 ML320, Grey 2010 ML350 (gas)
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Discussion Starter #7
I spoke to the manager of the garage: A second Mechanic at the shop believes that the new booster is bad. How he determined that, I don't know. The manager said the mechanic is sure the Master Cylinder is good, so the booster must be bad. They have ordered a new booster from Dallas and it should be here (Birmingham) by tomorrow (Thursday).

I'll update the thread with the results of the new booster.

It bothers me that I'm spending $2k on an ML that's probably worth $3k.(2002, 170k miles). Oh well...

-Brian
 

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I spoke to the manager of the garage: A second Mechanic at the shop believes that the new booster is bad. How he determined that, I don't know. The manager said the mechanic is sure the Master Cylinder is good, so the booster must be bad. They have ordered a new booster from Dallas and it should be here (Birmingham) by tomorrow (Thursday).

I'll update the thread with the results of the new booster.

It bothers me that I'm spending $2k on an ML that's probably worth $3k.(2002, 170k miles). Oh well...

-Brian
Brake booster will not fix excessive pedal travel.

Since search engine here is FUBAR I have used just generic Google query. "w163 soft brake site:benzworld.org"

Here are results:

First. Moderator of this forum @cmitch starts a new thread. Ends it with "Huh?" Really. https://www.benzworld.org/threads/very-soft-brake-pedal-2002-ml320.1537123/

Second. Again no resolution. https://www.benzworld.org/threads/2000-ml320-brake-booster-problem.1636295/

Another. Again. https://www.benzworld.org/threads/spongy-brakes.2076553/

Do I need to go on?
 

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1989 W124 260E
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I would put my money on flexi hoses .The booster can be checked by -first you start the car with your foot on the brake pedal now switch off the engine still keep foot on brake .Push pedal down a few times till it is on the floor boards ,hold it there .Next step is while your foot is still on the pedal with the pedal right on the floor start the engine up ----good booster foot lifts up as the pressure biulds in the booster . Bad booster foot moves very little or not at all .
 

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FWIW, my ML500 is about the same. Effective brakes - decently strong, but spongy pedal quite a bit softer than average. It works better than it 'feels'.

The E-wagon, w210 has both great effectiveness and great feel.

On the ML, I was thinking I have a bit of wear on the Master Cylinder & rubber hoses are flexing, too.

Matt in Australia had gotten a set of 4 braided steel brake lines he was going to install and let us know how they work.

Hey Matt, are you 'reading the Air-Mail' down under - did you ever test them out ?

Mine isn't so bad I'll tear into it. But keeping an eye on it !

Best regards - David in Texas
 

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2000 ML55 sold😢 2013 ML500,😁 2015 C250 estate wagon, 1927 Dodge 4 sedan, 1929 Dodge
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FWIW, my ML500 is about the same. Effective brakes - decently strong, but spongy pedal quite a bit softer than average. It works better than it 'feels'.

The E-wagon, w210 has both great effectiveness and great feel.

On the ML, I was thinking I have a bit of wear on the Master Cylinder & rubber hoses are flexing, too.

Matt in Australia had gotten a set of 4 braided steel brake lines he was going to install and let us know how they work.

Hey Matt, are you 'reading the Air-Mail' down under - did you ever test them out ?

Mine isn't so bad I'll tear into it. But keeping an eye on it !

Best regards - David in Texas
I ended up selling the ML55 before I fitted them but I gave them to my friend to install. I don’t know if he ever did.
 

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Oh, I asked him if he had bled the brakes and he said, "Yes".
You might want to check for recalls and Service Bulletins I found this
2002 Mercedes-Benz CLK320
  • RECALL: Abc High Pressure Hose. This may result in abc hydraulic fluid leakage near the catalytic converter. That would definitely make you pedal soft! If they screwed up one model odds are they did the same on another model.
 

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CURRENT: 2011 SL550, 2011 C300 FORMER: ML350, CLK550 Cabriolet, C240, ML320, 300TD
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You might want to check for recalls and Service Bulletins I found this
2002 Mercedes-Benz CLK320
  • RECALL: Abc High Pressure Hose. This may result in abc hydraulic fluid leakage near the catalytic converter. That would definitely make you pedal soft! If they screwed up one model odds are they did the same on another model.
Besides the fact that the W202 (2002 CLK320) was never offered with ABC, and ABC (ACtive Body Control) has nothing to do with the break hydraulics, this is totally irrelevant to the W163 ML.
 

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I state clearly a path to repair could be CHECKING FOR RECALLS & BULLETINS. WAS IT NECESSARY I get a rude email? FYI I Used my car as an example. The fact I don't know the person asking question skill level I thought an example might help.
 

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Red 1987 560SL, Silver 2002 ML320, Grey 2010 ML350 (gas)
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Discussion Starter #15
The mechanic now believes that the ABS Pump is bad and has ordered a used one from the salvage yard.

Anyone have any thoughts on this latest diagnosis? Will the ABS Pump cause lots of play in the brake pedal? Thanks for your response!
 

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2000 ML55 sold😢 2013 ML500,😁 2015 C250 estate wagon, 1927 Dodge 4 sedan, 1929 Dodge
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The mechanic now believes that the ABS Pump is bad and has ordered a used one from the salvage yard.

Anyone have any thoughts on this latest diagnosis? Will the ABS Pump cause lots of play in the brake pedal? Thanks for your response!
It’s very doubtful it will make any difference at all. I would be looking at the brake lines first as well. Get a set of verniers and place them around the brake hose in different positions and get someone to press on the pedal with the engine running and see how much they expand.
 

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The mechanic now believes that the ABS Pump is bad and has ordered a used one from the salvage yard.

Anyone have any thoughts on this latest diagnosis? Will the ABS Pump cause lots of play in the brake pedal? Thanks for your response!
So, where are we with this issue?

 
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