My 2007 SL550 with 110,000 miles and the ABC suspension has become abnormally stiff. And I mean super stiff. You can feel every crack in the road. Its horrible. The problem started slowly and became worse and worse over the last 3 or 4 years.
No ABC warning lights. No sagging on and of the struts. And I don't see any leaking fluid.

Truthfully I can't afford an expensive repair at the moment. I've read that changing the dampeners/accumulators could be the solution. Can anyone verify if this is true. And could I change just one of the dampeners and see an improvement before I risk spending the money to change them all?

 

If the accumulators are bad, which they probably are, driving it probably will get you to a very expensive hose repair. There are pressure drop tests that can be performed to verify accumulator health, but they are wear items and probably bad on your car at the age and mileage.

 

What @cdk4219 said. ☝️

Accumulators act as pressure buffers to the hydraulic lines. They are ball-shaped things that have an air bladder inside. If that ruptures, they fill with hydraulic fluid and then the hydraulic hoses take all the shock pressure. They weren't made to do that.

 

They are wear components like brakes, and 100k is about when they go, probably shorter if you don’t change the fluid regularly (30k miles). Yours are shot. The longer you drive it like that the more expensive will be the repair, we can all basically promise you. Change them all, the fluid and filter with them. Cost of ownership, ignore it at your peril (as you’ve been doing). Hope you haven’t pulled the pin on the grenade yet. What you’ve been doing is how these systems go bad.

maw

 

While accumulators are failure prone, they don't cause stiffness in the suspension. Since it has been a progressive issue, I would start by checking the condition of your front suspension. At 110k miles, you could have bad ball joints, bushings, and strut ball joints. If you have some play in the suspension, you might be feeling some of that. Also, check for any ABC codes and check values on all of the acceleration sensors. A bad acceleration sensor can cause some very strange and aggressive behavior. I'm not sure that it would fail in a progressive manner like you describe, but still something to check.

Without the active actuations, the struts themselves are very soft, so I think that the systems is either over responding or you are feeling some mechanical suspension issue.

Does it raise and lower properly with the height button?

 

My (limited) understanding is that if all accumulators fail, there is nowhere for the pressure to go upon hitting a bump in the road, and therefore the suspension will be super stiff. Is this not the case?


Yes, raises and lowers to the full and proper hights for each level. However the speed at which it rises is 2 to 3 times slower than when the car was riding perfectly. Lowering is at full speed.


The front and rear suspensions are equally stiff. Could i conclude from this that it's probably not ball joints, bushings, or strut ball joints, since they would have to fail at the front and rear simultaneously and progressively fail at the same rate. (which I assume is not likely) ?

 

cdk4219, JettaRed, maw1124 thanks for the info. Greatly appreciated. Yes, i can see that this is an issue not to be ignored or it will get very expensive very fast.

I've found some used accumulators on ebay and some videos on how to replace them on youtube and plan to do it myself. (Can't afford a professional at the moment)
Question for you all... Is an extremely stiff suspension almost certainly due to failed accumulators? Is there any other symptoms or signs I can look for to be sure the accumulators are the cause?

 

Used accumulators?

 

While these things have doubled in price over the last 6 years (and ain't cheap), I would be very skeptical of getting used accumulators anywhere. There is a bit of labor required to replace them and you don't want to be doing/paying that more than once.

If the ride is jarring when you go over a pebble in the road while the car is at a normal ride height, then I don't know what else would cause the stiff suspension.

 

The main accumulators are on the supply side so they don't act to soften the suspension. They aren't really necessary until the ABC gets very active like on a very bumpy road and I've never been able to diagnose a blown accumulator by ride quality. ABC1 does have a rear accumulator on the return side to prevent excess pressure on the return, but it would only be necessary in extreme situations and was eliminated on your ABC2 system. The quick test for accumulators is to compare dipstick readings with the engine off and engine running. There are separate marks on the dipstick for both conditions. If you don't see a change, or see a change of about half the distance between the marks, you have blown accumulator(s). If you see a change roughly equal to the distance between marks, than fluid is being stored by the accumulators and they are intact. Note that it takes awhile for fluid to drain back when you stop the engine, so give it five minutes or so, wipe the dipstick, and recheck.

There are not a lot of ABC components that affect all four corners. Basically the pressure supply, the control, fluid, and the acceleration sensors. The fact that it raises slowly is probably a clue. Pull a sample of fluid and make sure that color and viscosity matches fresh Pentosin. I don't think it is a pressure supply issue as you would be getting dashboard warnings. I am concerned that a bad acceleration sensor is making the system 'hyperactive'.

Normally suspension wear would tend to make the system more sloppy and not stiffer, but with ABC, the system is trying to control level. If you are getting unexpected level changes from bad control are bushings, for example, ABC might be overreacting to try to compensate.

If you do decide to try used accumulators, make sure that you buy the correct ABC2 versions. Most of the ebay listings will be for '03-'06 ABC1 systems.

 

USED accumulators seems insane to me. New ones don't cost much. You're doing the work to replace them, why put used ones on the car. Get new ones from FCPeuro website and once installed, you won't have to worry about them again for at least 10 years or 100K miles.
Wait too long and if you have a bad accumulator you're stressing the hoses and could blow one, that's what I did. However, I'm glad because that was the "weak link" and now that is new as well, although of course that meant spending more money... but now the car couldn't be happier, and since I love it, I'm happy too. It is just like a new car. It's one of those cases where I have more into it than I could get if I sold it, but since I have no intention of selling it, who cares.
Replace the engine mounts and trans mount at the same time, that's what I did. There isn't a single part that I would buy used, to put on my car.
For new front accumulator FCPeuro charges $221, Rear $214, and pulsation dampener $209. And FCP guarantees those for life.
FCP do not seem to have engine mounts available but Partsgeek has available a Lemfoerder kit with both engine mounts and a trans mount for $199. So your total for all these parts would be about $843 plus tax and maybe a little shipping but you might get free shipping.
DO NOT take the car to a MBZ dealer!! They will rob you blind. If you can't do the work yourself, find a good independent shop that has a reputation to uphold and a zillion five star google reviews, and will install parts that you supply. This way you're not paying them to mark up the parts cost.

 

Do not buy a used accumulator, they are most likely failed.

you can do fcp, or autohauzaz $150 a pop but no lifetime.


https://youtu.be/Ot9FxRmAMVo?si=L2p1aUW-iO2Cq6dL

 

I checked the dipstick and the difference between the engine-on and engine-off is exactly half of the distance between the upper and lower mark. So that means 1 of the 2 accumulators is shot, correct? That makes a lot of sense because I do remember having one of the accumulators changed at around 80,000 miles.

So at this point, considering that 1 of the 2 accumulators is fine. And also considering your explanation, MikeJ65, that failed accumulators should not cause stiff ride. It seems fair to conclude with certainty that the issue is not with the accumulators. Correct?

I also started paying close attention to the nature of the stiffness. It's a bit strange. At very low speeds, like in a parking lot, I can feel every crack in the pavement. But on the freeway it actually feels much smoother. Not normal by any means, still stiff. But if I can feel a tiny crack at low speeds, you would expect at highway speeds, bumps & dips should be absolutely brutal. But they're not. The car almost rides smoother on the highway. Similarly, speed bumps in a parking lot are not horribly brutal. Definitely stiffer than normal, but not brutal.

MikeJ65, you suspected there may be some "play" in bad ball joints, bushings, or strut ball joints. It seems this could exactly explain why I can feel small cracks. If the rubber has deteriorated in these joints, any small crack would cause metal on metal "play". Larger bumps would cause the same amount of "play" but not any extra. And considering a bump is far larger than a crack, it would feel almost smoother in relation to the size.

And the fact that all 4 corners of the car have this issue is probably due to the fact that I've ignored it for so long. Long enough for the problem to develop in all 4 corners.

(Also, side note...
The overall ABC fluid level was a bit low. About an inch lower on the dipstick than it should be. I know for certain I topped off the fluid about 2 years ago, when it was also about an inch low, so there is potentially a slow leak somewhere in the system. Not sure if this has any significance.)

 

Thanks everyone for setting me straight on used accumulators from ebay. Yeah, clearly a bad idea. And thanks for the tips on buying from FCP or Autohauzaz. Their prices seem very reasonable.

And a huge thanks to everyone contributing to this thread. You guys have an awesome community here and I highly appreciate everyone taking the time to help me! Keep the advice coming. I'm all ears!

 

My experience has been that usually blown front accumulators will cause an intermittent ABC warning when you hit a sharp bump, but rears do not. I'm not saying that is 100%, but I think that with the front out, you see more pressure drop at the pressure sensor (much closer to the front valve block) and that is what triggers the warning.

I would find a good independent shop that specializes in Mercedes and have them check it. Then you will at least know what you are facing as far as repairs. The strut ball joints can be replaced, but usually if they are bad the strut cover, top cushion, and hose are all getting to the point of needing replacement. A full front end rebuild can also get fairly expensive. Early cars don't have replaceable upper ball joints, so you might have to buy the entire upper control arm and the same is true on the front strut arm. Between struts, upper control arms, lower control arm bushings, lower rear ball joints, and front strut arms, you are looking at a sizable expense, but that is likely what it really needs.

If this is a daily driver that you rely on, my advice would be to sell it and buy something with better reliability and lower maintenance expense. The R230 is not a good car for a tight budgets and it may cause you more grief than enjoyment. If it is just a fun car and you can do repairs as your budget allows, that's another story. The front end work is not all that difficult, but it does require some special tools and moderate mechanical skills. Not really something you should take on if you don't have a decent amount of experience.

 

Hard to admit, but I couldn't agree more.

Generally, the R230 is a rock solid car EXCEPT for the ABC, Vario roof, gas pedal, gas tank baffle, shifter mechanism, and sometimes the transmission conductor plate sensors. I didn't have a roof problem, but I did with the other five items. They were all easy fixes except the ABC system kept having problems. Eventually, I traded it for the R231 and couldn't be happier. Of course, the R231 is 11 years younger than the 2004 SL500 I had, so we will see how she holds up.

Edit: Add the pneumatic trunk locking mechanism.

 

Especially when dealing with the ABC