2003 SL500

Took my car in today to diagnose why it’s suddenly dropping when idled with the car on. My thinking was one of the ride height sensors have gone bad. Or maybe another ABC sensor but the SDS did not find anything except low fluid.

My mechanic did a rodeo to get air out of the system And refilled the reservoir with 1 quart of ABC fluid but then he told me that the reservoir ended up overflowing and this is a sign of a bad accumulator. I’m set to go back on Monday for him to change a bad ball joint and he said he will check out the accumulators and make sure everything is good but he’s certain that it’s either the accumulator or maybe even the valve block.

i’d like to get some feedback from the forum on this issue. Is an overflowing reservoir a symptom of a bad accumulator?

What about the car dropping on its own when I’m at a red light or sitting in my car parked idle? In a 30 minute drive, the car drops 2 to 3 times when I’m waiting at a red light/idle. You can feel the car lower on its own really quickly.

thanks

 

There is not any sensor for fluid level. SDS cannot give any code for fluid level.

If the fluid gets too low, the system will have low pressure. This will be visible in SDS and will result in the red ABC DRIVE CAREFULLY message on the instrument panel.

Maybe this guy didn’t know what he was doing and just overfilled it.

I would monitor the height values in SDS while the dropping occurs. Does the car think it’s higher than it actually is (height sensor problem), or does the height value look ok when the car drops, the car realizes there’s a problem and then raises itself back up (control valve problem)

My money is on a bad/dirty control valve.

 

If fluid is shooting out of the ABC reservoir, it often means there is air in the system and needs to be bled correctly.

 

you sure about that?

 

I’m sure that it is often the root cause. It just happened to me a couple of months ago on my SL55 AMG, improperly bled by my Indy. I’ve read about this happening to other folks, too.

 

Reportedly a failed accumulator can cause fluid to briefly overflow the reservoir as compressed nitrogen gas expands and reaches the reservoir. You can identify a failed accumulator by testing them with Star Diagnosis.

It could be a ride height sensor. It could also be one of the five acceleration sensors. Any sensor can be faulty and yet not register a fault.

You can see the value of a level sensor change abruptly, and I think the challenge is to discern whether it is the cause or the effect of the abrupt change in chassis level. To do that I would go into the Star Diagnosis development menus and chart the value of the relevant level sensor and plunger travel sensor. A plunger travel sensor represents the ABC controller's output to a strut control valve, so if it's change leads the change in the level sensor, then the level sensor is not the problem, as it simply responding to the ABC controller action and not causing it.

Star Diagnosis explains how to test the acceleration sensors. You get the chassis to move in a periodic motion and watch for the action to register on the related sensor. But since the abrupt dropping is intermittent, it seems unlikely to me that such a test would identify a faulty acceleration sensor.

 

Bob- you’re awesome

I remember many years ago I had this same issue on my CL 500. When idle or at a red light, you can feel the back of the car drop. I drove around like this for close to a year and then decided to finally get it diagnosed right before the warranty was up. I took it to the dealer and told my service advisor and he knew exactly what I was talking about. If I remember correctly some sensor in the back was replaced and I never had that issue again.

I decided to try a new mechanic that’s near my house since the one I normally go to is a little far and a little bit more expensive. These guys were OK but I just don’t think they took the extra steps to figure out what’s going on. So I decided to go back to my original mechanic and I’m scheduled to be there on Tuesday. Hopefully he can point out why the car is dropping. I may even have him just diagnose everything like the valve blocks just to make sure we’re good.

i’m going to have him also change the rain sensor in the windshield because I’m sick and tired of getting light sensor visit workshop. Also need a new lower driver side ball joint.

i’ll keep everyone posted. Thanks for all the feedback. I try to educate myself as much as I can before instead of just throwing money away and having someone play a guessing game at my expense. I like to do some background research before walking into a mechanic shop. It’s funny because they try to explain things to me like a kindergartner when it comes to my car and then I stop them and say things like “oh yea the psi level is supposed to be....and rodeos is required after a flush etc...” and right there and then they know that they can’t pull a fast one on me because I know these cars (for the most part)