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Hey all. I love my 2005 SL55 AMG with 60K miles. I know the Active Body Control is problematic but have decided to keep the car and maintain the ABC, etc. as best I can. (Cheaper than buying a newer SL AMG with a warranty.)
FYI, so far, within the last 10K miles, my independant shop (San Diego County) has done the following maintenance:
Problem: Pentosin mixing between power steering and ABC reservoir and overflowing the tank.
* Replace power steering reservoir filter and fresh Pentosin.
* Replace front and rear ABC pressure reservoir cells.
* Replace ABC pump and reservoir, fresh filter and Pentosin. Rodeo test.
Two weeks ago I noticed that the ride height is becoming uneven from left to right (like others with ABC). I took the car to my indy. They used their software to level the car. They said the adjustment was only minor. However, this week after sitting for 5+ days, looking at the car from behind, I see the car is lower on the left side than the right. (I know that is expected to some degree).
I checked the ride height of all four corners with the car cold and after driving 30 miles. I measured from garage floor to apex of the wheel well. I've made a graph (see below). Though I am aware of the info at the link below*, I thought I'd share this graph in case anyone here in-the-know can point to a possible culprit, e.g., a front or rear valve block, or ride height sensor for example?
I really doubt that valve blocks are the reason - it is very unlikely that both front and rear would have the exact same problem, besides, front never levels.. The difference of .125" measured at the rear after the drive could be due to the floor being uneven, so I recommend to repeat the measurement with car facing the opposite direction. Also I would try to leave car at different height settings and see, if problem exists at high and low settings. My car sometimes (not always) leans to the right after sitting for a while, but only at the rear, not the front, so I can say that crooked back end does not affect the front end. It may be possible, that having front end crooked (since front is way heavier), would over time force rear end to change height as well. In favor of this theory is the fact that rear levels (or almost levels) after drive, but leans after sitting for a while. Front is never level, so I suspect that ride height sensor (or setting) is the problem. My car levels as soon as I start the engine and cycle it up and down.
I really doubt that valve blocks are the reason - it is very unlikely that both front and rear would have the exact same problem, besides, front never levels. . . . It may be possible, that having front end crooked (since front is way heavier), would over time force rear end to change height as well. . . .
So my chart points to a front ride height sensor eh? Question is, is the left low or is the right high? I guess both sensors need replacing to be sure. I assume I can't just swap the part out since the suspension has to be re-calibrated?
I also didn't know that parking the car in various height settings could point to an issue. Does anyone know if this also includes having it in ABC Sport vs. Comfort modes?
I think an uneven floor can be ruled out. The slab is dead flat perpendicular to the car's axis, and is sloped for drainage (0.25" per foot) parallel with the axis. In addition, the measurements are relative anyway, i.e., slab to apex of wheel arch. However, I will turn the car around soon just to check. (Pardon the lens distortion in the pic.)
If anyone can answer some of these questions, I would be very grateful. Thanks again.
Last edited by RProsser; 03-01-2019 at 10:52 AM.
Reason: Clarify a misunderstanding.
having a ride height variation is pretty common on all cars.
many tracked cars do corner balancing, where shop will raise or lower each corner based on weight of each corner, NOT by height of each corner.
have you measured ride height per corner of your 911? is it perfect both side?
are you having any handling issue?
it also look like you are measuring from fender arches? standard way of measuring ride height is pinch weld height (or somewhere alongside bottom frame). this is to eliminate body panel inconsistency.
btw, 51/49 weight distribution has nothing to do with left to right height. also that corner balancing is to balance weight diagonally, NOT side to side.
having a ride height variation is pretty common on all cars...
...many tracked cars do corner balancing, where shop will raise or lower each corner based on weight of each corner, NOT by height of each corner.
...are you having any handling issue?
bellwilliam: Thank you so much for your response. Yes, I am very aware of what corner balancing is. I've tracked cars and have been around sports & race cars since I was a kid. Thing is, with this one, recently its stance from behind is starting to look very wonky. Something somewhere is reaching the end of its service life? BTW, It handles fine -- no issues to speak of. I just want to level her out so she doesn't look like she's listing to one side. It bugs! LOL
I guess we are having communication difficulties. What I meant was that according to your measurements, your front is never level - neither cold, nor after run, while rear is almost level after run.
You need to measure it at the calibrated level to get a base line. When you go in with the SDS you can choose the actuation to automatically adjust the ride height to the calibrated level. As stated before the ride height may vary slightly depending on many things. When you choose that actuation you can then take your measurements. This will rule out any error in ride height calibration. If your cars ride height was calibrated 0.5" off side to side then perhaps what you are seeing is normal based on the calibrated level. Hopefully that makes sense. That would also give you an idea if one side is lowering or one side is raising. I wouldn't be replacing ride height sensors unnecessarily.
. . . As stated before the ride height may vary slightly depending on many things. When you choose that actuation you can then take your measurements. This will rule out any error in ride height calibration. . . .
knowbenz: thank you very much for your input. So, perhaps it has lost its calibration for some unknown reason. Let's hope so. If that's the case, is it best to conduct an all wheel alignment and corner balance using the Star Diagnostic Scanner available to an indy shop? Or is this kind of chassis fine-tuning best done by the dealer since they have access to the very latest software? (I've been told by some shops that only the dealer can fix certain things.)
Regarding your quote above, when you write "choose that actuation," exactly which actuation are you referring to?
knowbenz: thank you very much for your input. So, perhaps it has lost its calibration for some unknown reason. Let's hope so. If that's the case, is it best to conduct an all wheel alignment and corner balance using the Star Diagnostic Scanner available to an indy shop? Or is this kind of chassis fine-tuning best done by the dealer since they have access to the very latest software? (I've been told by some shops that only the dealer can fix certain things.)
Regarding your quote above, when you write "choose that actuation," exactly which actuation are you referring to?
Thanks again!
If you have an SDS under ABC > actuations > "move to calibrated level (automatic)"
Due to it being an active suspension and constant fluctuations, when you pull into your garage your car may not be sitting at the calibrated level. When you calibrate the ride height ideally you measure like you have done and make them equal side to side. In theory when you are turning and moving the car around it should return to that calibrated level but that isn't always the case, which is why if you cycle the ride height switch the car will attempt to go back to that calibrate level and you have a better measurement. It may not go all the way back to calibrated level though, which is why on any ride height complaint I always actuate it via SDS back to calibrated level, you can watch the sensor change as this happens. Once you know for a fact it is at the calibrated level you can measure it properly for a base line and be able to tell if the change in level is from lifting or lowering. For all you know the last person to calibrate it may have just eye balled it with one shoe on.
They don't simply loose calibration, you are supposed to recalibrate after sensor or strut replacement. You can have physical damage or tampering to the linkage arms or sensors. The arms mount to small metal tabs that are easily bent one way or the other. It only takes about 1/4" change in length of arm for about 1" of ride height change.
But I wouldn't spend any money based on my post. I don't see any major concern with what you are describing so as long as you don't have any leaks I wouldn't get too crazy about it. If you have an SDS check it there, if not then next time you go by the shop have them check it for you
knowbenz: thank you for your continued interest in my post. FYI, the car has never been in a shunt, nor do I have any reason to believe that there has been any physical damage to a suspension member. That said, I admit that the potholes here in La Jolla are brutal, and the car rides on 20" rims, but knowing the rigors of how Mercedes-Benz tests it's cars during development, it's hard to believe that a pothole could knock a sensor out of adjustment?
On SDS: I have stayed away from "experimenting" with this car. I'm used to wrenching on older, more analog cars, but maybe I should invest in a Merc SDS reader. Or, just say eff-it and find a good shop/competent dealer. I write that because I realize this SDS tool takes some time to get to know the intricacies and I hate to screw something up as I learn.
knowbenz: thank you for your continued interest in my post. FYI, the car has never been in a shunt, nor do I have any reason to believe that there has been any physical damage to a suspension member. That said, I admit that the potholes here in La Jolla are brutal, and the car rides on 20" rims, but knowing the rigors of how Mercedes-Benz tests it's cars during development, it's hard to believe that a pothole could knock a sensor out of adjustment?
On SDS: I have stayed away from "experimenting" with this car. I'm used to wrenching on older, more analog cars, but maybe I should invest in a Merc SDS reader. Or, just say eff-it and find a good shop/competent dealer. I write that because I realize this SDS tool takes some time to get to know the intricacies and I hate to screw something up as I learn.
Thanks again.
A lot of options in LA SoCal area so you shouldn't have an issue, ask around your area and I'm sure you will find a great shop.
I write that because I realize this SDS tool takes some time to get to know the intricacies and I hate to screw something up as I learn.
I don't know of anyone on any forum who has screwed anything up using SDS. For one thing, you can learn offline with the software simulating the existence of a car you are diagnosing. And the time it takes to become familiar with its use is probably much shorter than you think.
In addition to what others are saying as to possible issues - here is how to best measure your height to reduce errors from tire pressure and not measuring perpendicular.
1. Set one end of a level on the floor and slide it next to the tire so that it is centred on the wheel hub when plumb.
2. Put a piece of green easy release paint tape on the outside of the wheel well where the level intersects it when plumb and centred on hub
3. Measure up from lowest part of wheel rim (not the floor) to the wheel well where the tape edge reflects centreline of hub.
This is accurate and repeatable for your car and between cars with same tire/wheel dimensions. To compare between cars regardless of tire/wheel dimensions - measure from centreline of hub to edge of tape.
I set mine so that all 4 corners are the same with driver in the car.
02-28-2019, 01:10 PM
