Originally Posted by JohanSL

Hi guys

I want to replace my pulse damper but now I'm confused, I understood you just take the old one of, fit the new one in its place and everything will be fine, now I read in this thread that there can get air in the pump??

1) How do I prevent this?
2) How do I release the system pressure before I remove the pulse damper?

Originally Posted by taleb659

My 2002 S55 has been acting up for some time. First it had symptoms of the rear sagging overnight. So I successfully rebuilt the rear valve block and no more sagging. My next problem was a constant LOUD HUMMING noise when driving the car. I knew right away it must be the pulsation dampener.

To determine if your pulsation dampener is faulty is actually very simple. You must first raise the front of the car off the floor. Wait about ten minutes to ensure there is no pressure within ABC system. Take off the plastic covers below the car. The pulsation dampener is located near the right passenger side wheel. If I remember correctly you must use a 24MM wrench to remove the pulsation dampener. It looks like a small black cannon ball. Once the pulsation dampener is removed take a regular sized ink pen and drop it within the ball. If it falls more than half way than your pulsation dampener is faulty.

Once I did this quick test I ordered the dampener, it was about $150.00 and one liter of CHF 11S which is about $20.00. I installed the dampener the same way it came off and filled the ABC reservoir to the proper level. I then loosened the belt and primed the pump.

DO NOT LET YOUR PUMP INGEST AIR! WHEN CHANGING THE DAMPENER AIR WILL BE INTRODUCED INTO THE SYSTEM. SO IF YOUR NOT CONFIDENT AND DO NOT HAVE THE PROPER TOOLS THAN LEAVE IT TO SOMEBODY WHO KNOWS ABC. I CANNOT STRESS ENOUGH HOW SENSITIVE THIS SYSTEM IS.

After everything was installed I performed a RODEO with my SDS and then changed the filter. GUESS WHAT?? No more humming sound and the ride is quite nicer. I will snap some pics of my faulty dampener and show why it was faulty.

Originally Posted by w4sim

Do you know what a bad wheel bearing sounds like? Its gives a constant humming sound above 20mph which gets progressively louder as you increase speed.

A bad pulsation damper will sound exactly the same but will start making the humming noise as soon as you set off and gets progessively louder with engine revs rather than speed. The best way to tell is to drive your car at 40mph, then put it into neutral and see if the noise drops as the revs drop. If it does, then its your pulsation damper, if it doesnt then its sdomething else. This is assuming your getting the humming noise to start with. Another side effect of a bad pulsation damper is the constant little vibrations under your feet. These should also disappear when rolling the car in neutral.

I did the pulsation damper first on my car and the imporvement in sound and vibrations changed the whole feel of the car. The engine mounts and tranny mount didnt make all too much of a difference, but i think a combination of all 3 things did not help the car at all.

In your case i would suggest changing the engine and tranny mounts first and then see how it goes for you. If you dont see a massive imrpovement then replace the pulsation damper aswell. The pulsation damper wouldnt really give a lot of vibrations of idle anyway, more so when your driving.

Hope thats of some help.

Originally Posted by Sebmel123

I have an 03 s600 that has similar symptoms...a humming/whining noise that seems to come from under my feet when I drive my car. No noise at idle and seems to to get a little higher pitched when I accelerate. Lastly, ABC light will come on after going over some bumps but will clear itself after starting car again..maybe unrelated. Tried your suggestion...drove to about 40mph and put it in neutral and the noise seem to go away. My ride also seems abit stiffer than I expected...have not owned the car very long but not certainly the smooth ride everyone talks about. My question is, does this sound like the dampener you were talking about and would mine (2003 S600) be located in the same area, as seem to be reading conflicting information?

Originally Posted by w4sim

Yep, definitely is the Pulsation Dampner. And yes, its also in the same position as well (on left hand drive cars, its under the passenger side footwell).

Whats the conflicting information your getting?

Originally Posted by Sebmel123

Thanks, new at this and still trying to make sense of all the information online on this matter. I appreciate the confirmation and sounds like it would be easy enough to order on eBay and replace. Can anyone who has done this state that it also helped to loosen up the overall ride of the car...mine seems a little stiffer than I have read it should be? Or, is this a different issue usually?

Originally Posted by w4sim

I can definitely confirm that my ride became a lot softer immediately after the change. Im sure a few others have reported the same.

If you think it hasnt, then theres another 3 of these spheres (cannon *****) you can change as well. But this one is the main culprit.

Originally Posted by Renntech6509

For the W221 do you have to raise the car off the ground to replace the dampener that's on the pump itself? Also, how much fluid is lost and will you get air into the system replacing this? I'd like to do it myself but don't want to screw anything up.