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.

Welwynnick

Very nice work, taleb.

Could you also elaborate on what you did with your valve block?

Did you just clean the valves out, as some do, or did you replace the O-rings like Howard?

Thanks, Nick

w4sim

My car has recently started humming aswell, usually gets louder as the engine revs get higher. At first i thought the exhaust had started leaking, so had it checked and it seems alright.

Then i thought it might be a wheel bearing as it does get louder as it gets faster. But 2 things to rule that out. It starts to humm as soon as it sets off, whereas a wheel bearing usually starts humming at around 30mph. And next, i noticed its humming with the engine revs, but even when in neutral. So im thinking its something engine related.

However, it does seem to be coming from the front of the car from underneath. If its the dampner then will it get louder as it gets worse or does it just stop at a humming noise regardless of how bad it gets now?

I probably would be able to take it off and put it back on again but im not all that confident with the rest of the system and so dont want to end up destroying anything. But if theres anything i can do to self-diagnose it then that would be a great help?

Thanks.

taleb659

Thanks Nick, regarding the valve block I purchased a bottle of odorless mineral spirits and disassembled the solenoids from the valve block. Make note of where each solenoid goes (FB1, FB2) Then soak the valve block in the mineral spirits for ten minutes and then blow the valve block out with compressed air. Do not soak the solenoids in mineral spirits. I used a clean soft bristle tooth brush and dipped the head of the toothbrush in mineral spirits and then thoroughly cleaned the solenoids. There are two small solenoids that have a piston and a spring. Remove the piston and spring and blow the solenoid with air. Mine was dirty which caused the solenoid piston to stick. Replace all the o-rings, you can buy a set very cheap at this link: http://allorings.com/cgi-bin/Catalog...playNumber=369. You need the BUNA N O-RING KIT which is on sale for $10.00 plus shipping. Then upon assembly dip the solenoids in CHF 11S OR equivalent, and assemble the way it came out. Then follow this procedure for filling and bleeding the ABC SYSTEM:http://ww2.justanswer.com/uploads/mb...ABC_system.pdf

If this was the cause of your sagging car lol, then it should not sag any more.

taleb659

W4SIM, regarding the humming, it will get worse and cause a very soft vibration.This is what I experienced with my car and I started to really dislike driving the beast. Taking off the pulsation dampener is very easy, the hard part is making sure the pump does not ingest air.

What I recommend in your case is to take off the lower cover and find the pulsation dampener. Take a good sized flat head screw driver and gently press the tip against the dampener with the engine running. Put your ear on the other end of the screw driver and if it is the same humming you hear in the car then you found the problem. However if your not confident in finishing the rest of the ABC bleeding procedure then take it to somebody who is knows there ABC system. Otherwise you will of been more than happy to hear that humming.

OCKlasse

From what I've read, it's an easy take the old off and swap the new one on, and rodeo isn't necessary afterwards. Do you feel a rodeo is necessary?

taleb659

No the rodeo is not necessary but my fluid was flushed 10,000 miles ago and I figured since I was doing the valve block and pulsation dampener it was a good time to buy two filters and trap any contaminant within the system. I then did the rodeo twice with the first filter. That way any contaminant would be trapped within the first filter, and then I installed the second filter and continued as normal. I look at it as cheap insurance .

jnash

Taleb, thanks for the great info. I have a spare valve block and have just ordered the O-rings from the link above and plan to keep one on hand as a spare. I was just curious, did you research those BUNA N O-RING KIT to ensure they meet the spec for the pressure and heat for the ABC suspension?

w4sim

To be honest i am beginning to kind of dislike driving it. Im not quite sure just how long ago it started but my brother pointed it out about 2 months ago, pretty much straight after the back end had been jacked up (if that has anything to do with it), and since then its been very noticeable indeed. I dont drive my car all too much nowadays so cant really say for sure wether its getting louder or not, but i suppose only time will tell.

The genral nagging i have always had with my car, for the last year and a half, is that its always vibrated when stood still at idle. Kind of like a small misfire from the engine. Iv changed the spark plugs and that didnt make it any better but now im sure its either the engine mounts or the transmission mount. Im now wondering if it was the pulsation damper all along and now finally its just given up. Or worse still, all 3 things. This could end up being a very expensive start to the new year.


One of these days when the weather isn't too bad i suppose i could get underneath it and have a look, go from there i suppose. I for one am looking forward to any pics you might post about the damper.

But so far, many thanks for your help and advice, it is really very much appreciated.

jnash

Engine mounts make a huge difference on the smoothness at idle. I really doubt a bad pulsation damper would cause vibration, more just a buzzing sound.
Mounts are fairly easy to install.

w4sim

Problem here is im getting both, vibrations at idle and a buzzing noise . . . . . bye bye Headers

You say the mounts are not too difficult to install, iv been quoted $500 to supply and fit both mounts, but i can get the mounts for $150. Does $350 installation seem a bit much for something thats not too hard? Im sure the tech told me something about one of the pumps having to be moved out of the way or something similar?

jnash

the left is a bit harder than the right side. THe book value time is 2-3 hours so the labor is about right I would think. I have seen a tech do it on a c-class in less than 30 mins.
It really depends where you take it I guess

taleb659

The buna-n should be able to withstand the requirements of the ABC system. The buna-n are made for hydraulic fluid seals, petroleum oil seals, and transmission fluid seals. They are able to withstand -40 F to +250 F.

I actually plan on disassembling the rear valve block in the near future to see how well these seals have held up. While I disassemble the rear valve block I will try and take thorough pictures of the disassembly. In the process, I plan on changing the Air cell located in the rear valve block assembly. The part number for this is: 2203200415. It can be found at parts.com for $131.00 plus shipping. The price for this is very reasonable and you might as well change it if you plan on rebuilding your valve block. That is one of the biggest mistakes I made, but at least I can see how the seals have held up.

w4sim

My 2004 S55 has gone abit stiff in the way of suspension and is making a humming noise when i drive as i have mentioned in this thread before.

Im now biting the bullet and replacing the pulsation damper, however i had a few questions before i start?

1. Where does the air get in the system from, and how do you stop it?

2. Which belt do i loosen to prime which pump and how is that done?

I can take the damper itself off and get the new one on, but the middle bit is a bit vague and i dont want to miss a procedure?

Thanks.

mrbenzes

My local Stealer wants $240 for the damper and the websites im looking at wont ship this item..does ayone hae a website they have used that will ship this item?
part number 220-327-02-15
Mike

jnash

A quick google of the part number gave me this
https://www.carpartsdiscount.com/aut...ml?3593=339854

Ships in 1 day $176

mrbenzes

Thanks JNASH....I did some more searching too and found one here http://www.benzpartsforless.com for $134 plus shipping....by the way, i have another friend in Houston with a 2001 S55, his name is WBrian Fogarty...do you know him? he has some older 6.9 cars as well.
Thanks,

Mke

jnash

no. don't think so, what color is his S55?

mrbenzes

all black.

merc79

W4SIM, looks like I'm always running into your post when I have speculations on whats going wrong with my S55,lolz....but hey did you replace your damper first or did you do it after changing out your engine mounts and tranny mount?
Secondly if you had done your damper first did it make your vibration go away? I'm having a lot of vibrations on idle, no humming sound, but alot of vibrations, I know for sure my engine mounts are shot, and as well the tranny mount. LIke when I press the gas pedal down hard the car shakes abruptly on intially then settles down. But again I dont get a humming sound like you mentioned hearing. I know another forum member JNash mentioned it couldn't be due to the damper causing the vibrations,but I wanted to know what your thoughts were on it?
Thanks again buddy for your help.

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.

merc79

Thanks for the suggestions, I did what you told me and I had the windows rolled down and couldn't hear no sound or anything till I let go of the gas pedal at 40mph. But this is the thing, if I'm parked and I rev the engine up to say 2,000-3,000 rpm the whole car inside vibrates like a biatch. Only on sudden revving it vibrates a lot. Hopefully the Tranny and Engine mounts will solve this problem. We have been getting a ton of rain here in Florida for the last few weeks and its causing flooding in some areas and unfortunately the mechanic I"m going to his shop is located in a area where water likes to remain stagnant after it rains becoming a small pond, so now I'm pushed back till Wednesday to get her fixed

w4sim

Definitely sounds more like your mounts. A bad pulsation dampener would not shake the car if you gave it a sudden rev. A bad engine or tranny mount on the other hand would.

Like i said, get your mounts done before the pulsation dampener.

I used to get constant vibrations at approx. 70-80 mph, like i have a pulsating seat under me. Turns out these were the rear subframe bushes

Thing is, these cars are now at an age where most of the bushes and mounts are pretty much shot, so you can get all your wheels aligned, tyres balanced, idler pulleys changed and even struts changed if needs be, but as long as the worn bushes are still in there they will play hell with your desire to get a smooth ride. Only problem is, nobody really considers changing these parts. My advice is to get them all checked at a garage just to see how bad they are and then go from there. You could be surprised at whats under there now.

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?

Welwynnick

Its one of the easy jobs. Don't worry so much. By the time you jack the car up and put it on stands, the pressure will have dropped.

Unscrew the old one, and screw the new one in. Job done. You will hear a few funny noises when you first start up.

Nick