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Hi , I bought a ML320 cdi about a year ago. Since it had 250 000 km on the clock , i did a lot of preventative maintenance as in changed " all " the oils (diff etc) got new headlight units, front lower control arms and new shock absorbers front and back.
With the new shock absorber I also replaced the "sway bars " ... now the car handles like a dream !!!! ..that's the good news !
Immediately after replacing the front shocks the brake peddle got soft! You can push it down to the floor ,slowly but you can.
Well best guess was Master brake cylinder got faulty for some reason
Contacted MB about the cost of the master brake cylinder , living in Australia , they quoted $850 ....well you can get the parts by far cheaper in the US or Europe which I did ( the exact part / partnumber) paid approx $200
: replaced the cylinder with new ATE cylinder, pressure bleed it ..... same problem
Next best guess was calipers and brake hoses (front left and right, sourced overseas ) .... problem still there
I searched the forum re similar issues and found a few threads which basically pointed to ABS bleeding
I have a Icar scanner which unfortunately does not assist with the bleeding of the ABS module. That is the only thing I can't do
Is there any other way to bleed the ABS module ? first question
..and what else may I have overlooked ? It is rather frustrating ! In addition when you buy overseas it can take up to 8 weeks to get the parts. Still worthwhile looking at what MB charges for the exact same parts!
The brake performance is still good but it is not the way is was and should be .
Any ideas , past experience , how to fix the problem !
Hi , I bought a ML320 cdi about a year ago. Since it had 250 000 km on the clock , i did a lot of preventative maintenance as in changed " all " the oils (diff etc) got new headlight units, front lower control arms and new shock absorbers front and back.
With the new shock absorber I also replaced the "sway bars " ... now the car handles like a dream !!!! ..that's the good news !
Immediately after replacing the front shocks the brake peddle got soft! You can push it down to the floor ,slowly but you can.
Well best guess was Master brake cylinder got faulty for some reason
Contacted MB about the cost of the master brake cylinder , living in Australia , they quoted $850 ....well you can get the parts by far cheaper in the US or Europe which I did ( the exact part / partnumber) paid approx $200
: replaced the cylinder with new ATE cylinder, pressure bleed it ..... same problem
Next best guess was calipers and brake hoses (front left and right, sourced overseas ) .... problem still there
I searched the forum re similar issues and found a few threads which basically pointed to ABS bleeding
I have a Icar scanner which unfortunately does not assist with the bleeding of the ABS module. That is the only thing I can't do
Is there any other way to bleed the ABS module ? first question
..and what else may I have overlooked ? It is rather frustrating ! In addition when you buy overseas it can take up to 8 weeks to get the parts. Still worthwhile looking at what MB charges for the exact same parts!
The brake performance is still good but it is not the way is was and should be .
Any ideas , past experience , how to fix the problem !
Thanks and best regards from Australia
You're not confusing a sinking pedal with the hill-hold function? Does it do it with every press of the pedal or just sometimes? Mine activates hill hold on an incline and it sinks slowly to the floor, almost. But it rebounds on acceleration. Might be worth checking if its functioning properly if everything else seems OK
Last edited by BlackML550; Jul 23, 2022 at 09:00 AM.
.... thanks for the comment . ....do I have that function ? ..if yes where is it ? anyway I will check it out and let you know.
...well checked it out > Yes the function is there .
I tested the brake with esp on/off / hillstart on/off ... still got the sinking pedal .
Mine activates hill hold on an incline and it sinks slowly to the floor, almost
as to your car , why should the pedal sink ??? and that as you said almost to the floor ?
When you stop your car come to an halt, what happens then ? Do you still can push the pedal to the floor ?
As far a braking my car is concerned, it engages very quickly and effectively.
...but the sinking pedal was not there before !!!!
following your ideas then maybe there is a sensor not working , just don't know.
On an incline (facing uphill not downhill) If I'm stopped and with my foot on the brake, If I push the pedal harder (without releasing it) it sinks and then the brakes hold in position until I accelrate and the pedal releases and raises again. Whilst it is the locked position, it sits lower than the pedal would normally extend to and it feels loose.
I thought that function may not be working properly and that was causing your problem. Ive attached photos from the handbook.
When my 2008 ML320 CDI was new, the brakes were brutal. You could emergency stop in a very short distance and applying more pressure would bring in the ABS easily. This was the day I picked up the car from the dealership AFTER the brake recall June 27, 2022. The brakes have been spongy for some time despite having been bled several times by local brake shops. One shop returned it to me with the brake pedal going straight to the floor. I was able to improve them somewhat by getting up to 30mph and braking really hard. The ABS no longer engages and the pedal makes this whooshing sound when pressed.
Hi .... thanks for sharing your experience !!!! That is the exact problem I Have !!!! including the noise you showed in your video.
I recently got the local yearly road worthy check . For that I made the mechanic aware of the problem . The answer was : he has seen a few cars with the problem but it does not effect the braking capability.
Further , 2 weeks ago I got my recall check . All ok !.. I made the "MB" mechanic aware of the problem , he did a test drive , sort off acknowledged the problem but dismissed it as a problem coming to the same conclusion as the above mechanic.
As I mentioned in the very beginning of the thread, the problem occurred/started after replacing the front right shock.
I have the rear brake hoses on order and when replacing them I will replace the Master brake cylinder again !! and of course bleed the system.
As to the noise when pushing the pedal ... that needs to be further investigated. I live in country Australia/NSW, so specialist workshops are not readily available . There is a brake specialist some 200 miles away.
I let you know how I go ! Please keep me posted too
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Soft/spongy brakes ML320
