Joe Clare

Hi all.
i believe i have a damper issue as when the car is hot and in town traffic there is a rev defined whine. I have bought the damper but i have two questions:
Do you have to remove the pump to access?
When the whining happens and car is hot, if i turn engine off it is difficult to start again? If i let it cool down for a couple of hours all is quiet and car starts first time as normal.

Any help and advice would be appreciated.

Thanks

Benztech777

Did you get it fixed? A hard hot start is most likely your starter getting old but first check and test your battery. Yes you can replace the damper without removing the pump all the way. Only remove the top bolt and loosen the bottom bolt and pry with a long screw driver or pry bar at the place where the pump bracket meets the front of the engine. Do not damage the pump by prying on the middle of the pump body! this will get you just enough room to remove the damper. Good luck!

Joe Clare

All sorted. New damper and noise and hot start cured. Thanks for reply.

Benztech777

Thats good did you do it yourself? Most people dont know that that dampener is a wear item. Over time it loses its nitrogen charge. Mine had a awful noise and its completely silent now. I replaced my dampener about 6 months ago. Was the starter bad? Oh well I suppose it dosnt matter to me much its just that for the readers sake we ask questions about problems and after its repaired its nice to show what fixed the issue in the end. Its good reference material for others.

oxff

Guys, have same issue. Got car with horrible noise on low rpm (like under 2000) outside it's impossible to hear that but inside it's insane. I was thinking it's a broken engine mount, replaced them but sound is the same.
I'm pretty sure that this is pulsation damper and I'm thinking to replace it by myself. Have few questions:
- How to bleed pressure? (it's about 80 psi in the system when vehicle is turned off)
- Where to get a filter for ABC fluid? (Dealer trying to sell be whole ABC reservoir!) Have you guys replaced it?
- Do I need some special tools for that?

Also I want to completely replace ABC fluid. Thanks

Mark out West

Know this is late, but I just replaced my damper over the weekend on my W216.M156 setup. Perhaps the mounting is different for the non-AMG engine, but there was just enough space to unscrew the damper from above using the cast-in nut on the damper and wiggle it out. I had to remove the plastic air intake on the left of the engine and unbolt and move (slightly) the power steering and ABC reservoirs. No issue with pressure since the damper is on the return side of the pump. Letting the car sit a while should bleed off any residual pressure. I'd recommend hitting the base of the old damper with some brake cleaner spray prior to removal to blast away any crud so as not to knock it into the pump.

oxff

Hey I did mine too. I released pressure with xentry, then there is couple of bolts holding valves with damper attached, bottom platform is removable and there is also two bolts to remove metal one. After this it's possible to get access to the damper. 26mm wrench is needed,it's kinda special - thin and bent. Since dealer asked 54$ for the wrench I grind regular one.
Old pulsation damper was bad, no pressure at all. After attaching new one most of the whining noise is gone but still have some. What it can be? I want to flush fluid completely and decided to buy abc flush tool because I'm afraid any other way will be really messy. Did anyone flushed it without tool? Still can't get where is back line from the pump.
Also I'm thinking about rear damper, maybe it's also bad. Is any known way to test it without removal?

Mark out West

I'm in the dark. Is the pulsation damper not directly mounted to the top of the ABC pump on the non-AMG V-8? Or is it remotely mounted and connected to the ABC pump via a pipe/hose?

Also, there's a lot of confusion about what's pressurized with the engine shut off. The only residual pressure should be in the hydraulic lines leading from the valve body to each strut. The remainder of the system pressure is lost, including the pump, coolers, and accumulators and damper. The fluid in the ABC reservoir rises when the engine is off because the damper and accumulators empty under gas pressure.

That's why there's a bleeder screw at each strut - to relieve trapped hydraulic pressure in the valve/strut pipe prior to loosening the quick disconnect coupling.

oxff

I don't have experience with M156 but my expectation that ABC should be the same. In my case pressure accumulator/pulsation damper was attached to the valve system, I don't think I may call it a part of the pump.
With xentry I was able to see about 80 bars in the system with engine off. There is bleeder screws but I do believe that it's so much better to drop car with software and after doing it I didn't had any pressure on the accumulator.

I still have small whining noise and I'm concerned about rear pulsation damper. Do anyone know a way how to check that it's working without removing?

alexanderfoti

The pulsation damper is directly on the output of the pump, not on the return. Its function is to dampen the pulsing nature of the hydraulic pump output.

With the wheels of the ground and the engine off there is no pressure in the abc system after 30+ minutes.

alexanderfoti

W220/215/230 has it remotely mounted
216/221 has it mounted on top of the pump

you must clean the pump so that it is immaculate before removing the pulsation damper. MB says to remove the pump and bolt it in a vice upside own so that crud does not enter the pump when changing the damper.

alexanderfoti

You changed the front pressure accumulator, not the pulsation damper. The pulsation damper is bolted onto the top of the pump on your car.

Symptoms of bad pressure accumulators are intermittent ABC Red warnings and low pressure warnings when hitting speed bumps or undulations in the road.

oxff

Thanks for making it clear. You're right. I checked wis and I see another one on the top of the pump. I was thinking that there is only one pressure accumulator so-called pulsation damper, but I'm wrong.
There is 3 of those, one exactly on the pump, second on the front valve and third one I believe in the trunk.

I never had any warnings or red lights on ABC but horrible noise inside the cabin on low rpms. Front right side feels a bit soft (softer then left one at least). Some whining noise that likely from the abc pump in the cabin. Should I also consider pulsation damper replacement?

Also at this point I still don't understand where is back like from the pump to the abc reservoir. I need to flush my system, fluid dark as night.

Gordon Cooke

I have the same exact problem. Did you ever determine if it was the pulsation damper or the pressure accumulator?

Gordon Cooke

Do you know how to tell if it is the pressure accumulator OR the damper? I am being told my noise is a pressure accumulator but I think it may be the damper. Thanks

alexanderfoti

The only one that makes a groaning noise at low rpm is the pulsation damper.

Gordon Cooke

I guess I was given wrong advice! Thank you! what WOULD be the signs of a bad pressure accumulator?

alexanderfoti

Intermittent RED ABC warning popping up when hitting bumps or undulations in the road, and an overly soft ride.

Gordon Cooke

Also, does Hydraulic fluid flow through the pulsation damper? It looks like it does not but some are talking about bleeding the system after replacement.

alexanderfoti

It doesn't flow through it per se, it fills it up slightly and there is a bladder inside that resists the pressure.

Its not necessary to carry out a rodeo etc, but raising/lowering the car a few times is more than enough.

Gordon Cooke

Thank you so much! You have been very helpful.

alexanderfoti

No problem!

Icedillon

Benztech777

I did mine without removing the pump all the way. I think I removed the top pump bolt, well after taking the belt off first, loosened the bottom pump bolt and was able to pry the pump away from the engine just enough to get the accumulator out. Be sure to never pry the pump anywhere near the center, only where the thick metal is in the area where the bolts go other wise you will damage the pump. The CL W216 has the pulsation damper on the top of the pump from 07 and up. The pulsation damper is the number one cause of noise in the pump area. the number 2 cause will be from an ABC pump running dry and getting damaged. So if your system never ran dry the pulsation damper is the first thing to change. The damper has a rubber diaphragm in it about half way in the middle and it also has about 2000 psi of nitrogen gas. When the pump runs that rubber diaphragm acts as a shock absorber and dampens the harsh pulsations created by the high pressure pump thus making it quiet. In a similar way the front and rear suspension dampers act as a shock absorber and cushions your ride. When say for example the rear suspension is hard as a rock and there is no cushioning when you drive over a speed bump that is a sign to replace only the rear axle damper. I hope this sheds some light on the subject. Good luck.

Gordon Cooke