ansracing

really need your experiance and recomendations. i have a 2002 cl500, about 2 weeks ago the abc light went and started making a little humming noise at low rpm's.your at a stop and car is quiet as soon as you slowly step on the gas there is a rubbing noise you can hear inside the car( sounds like when you your brake pads wear out,the grinding noise) but go's away at about 2000 rpm's.took it to mercedes specialist said it was the transmission oil pump and would cost $4000 to repair. went for 2nd opinion else where and they said it was p/s pump because when you take off the serpentine belt the noise go's away.replaced that, noise is still there. finally took it to the local mercedes dealer they replaced the abc hose(recall)and the alternator(recall) and stated the noise was due to "worn motor mounts" and was $200 in parts and $1200 in labor.decided tobut the parts and have local mechanic rplace them... guess what noise is still there. Any body deal with this already, i love the car and it runs great but this kind of issues really aggrivates me.
thanks in advance

pboris

Did you ever get your issue resolved? I'm curious what the issue was.

I have this same problem with my 2003 CL500. On occasion, particularly when I first begin driving, I hear a slight growl or grinding, but it later subsides.

Today, as soon as I turned on the vehicle, it display red message saying "Active Body Control Drive Carefully". There was a more prominent grinding or rubbing sound, that seemed to coincide with the RPMs as they got higher. I turned off the ignition, checked around the vehicle, and restarted. The Active Body Control message went away, but I still hear the grinding sound.

s5benzo

In the abc system when things start to hum that points to the accumulators. Those are the black ball shaped objects on the abc system. They are nitrogen filled and absorb all the bumps from the road. When they go bad you will notice the suspension ride rougher and abc light come on intermittently. The way to tell they are bad is to take them off and put a screwdriver in them, don't force it in just set it in . If the screwdriver doesn't fall in all the way the accumulator is good , if screwdriver falls right in accumulator is bad . When these are replaced you will notice softer ride and hopefully the humming go away. It is advised to replace these accumulators when they go because you are putting all the strain on the hoses and abc components. Good luck , hopefully this cures your problem. I advise you to do some research as well.

pboris

Thank you for your reply s5benzo. All that you say regarding the suspension not absorbing all the bumps seems true. The humming is really more of a rubbing sensation with almost a grinding noise, but what I don't understand is why that noise seems to coincide with the revving of the engine. The higher the RPM, the more noticeable the grinding sound, particularly when you are going slowly and there aren't other highway noises. Would you still think these accumulators could be the cause?

If so, how hard is it to remove an accumulator and where would I find them?

s5benzo

http://www.benzworld.org/forums/w215...sues-more.html


http://www.benzworld.org/forums/w215...-steering.html

http://www.benzworld.org/forums/w220...cumulator.html

Here are a few links for you to look at and move forward. The first one is a sticky with all information on abc and problem /solutions. You can look at the diagrams to see exactly where the accumulators and pulsation dampers are. Good luck I hope you fix your issue

ctravis595

i respectfully disagree, i don't think it's the accumlators since it happens at low rpm. sounds like a bad ABC pump, bad bearings, bad pulley on the pump ETC

i could be wrong though

matias

Hey guys, for those who have the drone at low revs here is the solution to the problem;
https://mbworld.org/forums/cl-class-...blems-abc.html
The pressure accumulator cost me 116€ and is very easy to change, is the view behind the right wheel.

qnbenz

I've got the same problem. I'd like to take the one near the front passenger side off and check. Do I need to depressurize the system first? What happens when I unscrew it? Will fluid squirt out? Will the car drop down? etc...

Thanks,
qnbenz

llcoolbenz

It is certainly the accumulator(s). Whenever the humming increases and decreases with the rpms from lowest to about 2000 rpms before it disappears....its the accumulator. Easy to replace and it will fix it. You'll even enjoy a better ride condition. You do not need to depressurize the system. When you unscrew the accumulator, hydraulic fluid will come out. I had my front end on jacks, by the way. If the accumulator is bad, it will be filled with the fluid. You will obviously loose a certain amout so buy a can to refill it. It was as simple as changing a canister style oil filter. Use the proper open ended wrench. It will be tight. Be careful not to damage any lines.

Dsecen

did you have any luck resolving this? Mine sounds like front right suspension