rouble Shooting Summary:
Here is a cheat sheet to help determine the cause of a problem and what action to take. If you aren't interested in how the system works and just want to know what to do, this table should suffice.
The remainder of this document will give you details on how each component of the system works, how to recognize when they fail, and what courses of action to fix them. There is also advice on how to reduce the ownership costs related to the ABC system, how to maintain it, and other valuable information.
[TABLE]
<tbody>[TR]
[TD]Symptom[/TD]
[TD]Cause[/TD]
[TD]Action to Take[/TD]
[/TR]
[TR]
[TD]"Drive Carefully" or "Visit Workshop" appears for a few seconds when hitting a bump or dip in the road.
This may or may not be accompanied by fluid overflowing from the reservoir.
[/TD]
[TD]One or more of the accumulators has failed and is no longer supplying pressure to help fill the struts when needed.[/TD]
[TD]Pull and inspect the front and rear axle accumulators - each are part number 2203270115. Replace as necessary.
Given these accumulators only cost about $150 each, you should seriously consider just replacing them regardless of what you find, as a preventative maintenance investment. [/TD]
[/TR]
[TR]
[TD]One or more corners of the car sags or lowers when parked. [/TD]
[TD]Assuming there are no puddles of hydraulic fluid on the garage floor, then this is a dirty valve block. Usually gunk has built up on the seats of the valves (the shutoff valve in particular) preventing a good seal, so fluid leaks out of the strut and goes back to the return reservoir.
It is also possible the o-rings in the valve have deteriorated.
[/TD]
[TD]The first action is to change the ABC fluid filter, perform a procedure called a "rodeo" that exercises the system, and then replace the filter again. This will sometimes clear up the problem, at least temporarily. This will cost around $300. If the fluid is old, you should strongly consider having it flushed, which will cost another $200.
If the filtering fails, and if you are capable of DIY repairs, then there are write-ups showing how to pull these blocks and clean them. It is also a good idea to replace the o-rings just in case one of them is the cause. Cost for this procedure is less than $100. Results vary.
You last option is to have the valve block replaced. This will cost around $2,000, or around $1,250 if DIY.
[/TD]
[/TR]
[TR]
[TD]"Drive Carefully" or "Visit Workshop" appears on the dash every time you start the car and stays on. It never goes away[/TD]
[TD]There is a malfunction in the ABC system somewhere. The ABC system noticed a problem when starting up and has disabled itself, locking the struts in their current position. Depending on how low the struts are, this may result in what many people describe as a "tuna boat" ride.
Possibilities are:
- A loose connection to a sensor
- A sensor has failed
- The pump has failed
- The system has a fluid leak causing a loss of fluid, preventing the system from getting up to operating pressure.
[/TD]
[TD]Check the underside of the car for any signs of fluid leak.
Check the fluid levels in the reservoir. If empty do not attempt to start or drive the car. If you run the pump dry it will be ruined...a $2,500 repair! Go the parts store for a quart of "Pentosin CHF 11S" fluid and fill to the upper mark before starting the engine.
If the system is unable to hold it's fluid long enough for a drive to the workshop, then have the car towed.
Take the car to the dealer or a workshop with a Mercedes STAR diagnostic system (SDS). If the problem is not leak related, then you will need the diagnostic codes to determine what component is having the problem.
The remainder of this document has advice on where to go from there.
[/TD]
[/TR]
[TR]
[TD]"Drive Carefully" or "Visit Workshop" comes on the dash and stays. Stopping and starting the car sometimes resets things back to normal for a while.
[/TD]
[TD]Possibilities are:
- The pump is weak, resulting in inconsistent performance. Sometimes the ABC system reaches operating pressure, sometimes not.
- A strut travel sensor may be going bad. Some strut motion from driving gets it working again.
[/TD]
[TD]Take the car to the dealer or a workshop with a Mercedes STAR diagnostic system (SDS). It will
have diagnostic codes indicating the problem.
If it is the pump, low pressure error codes will have been logged.
Confirm by
- Rule out accumulators with SDS diag test
- Monitoring pressure during a rodeo. If it can make it through the rodeo without the pressure dropping below 100 bars, the pump is fine.
A strut sensor problem will have error codes logged for it as well.[/TD]
[/TR]
[TR]
[TD]You hear a loud bang, and the "Drive Carefully" message comes on the dash shortly after.
[/TD]
[TD]A hose has blown, and the system has run out of fluid.[/TD]
[TD]Pull over and shut off car immediately. Check for leaks under the vehicle (they may be masked by the plastic panels covering the underside). Check the fluid level in the reservoir. If empty do not start or drive the vehicle. Doing so will ruin the pump Have the car towed to a repair shop.[/TD]
[/TR]
[TR]
[TD]You can hear and feel a vibration in the floorboard, brake pedal, gas pedal, shifter, and elsewhere. Occurs at low rpm, around 1250 or so. Is present both in gear and out of gear. Most noticeable when maneuvering around a parking lot at slow speeds. The problem usually comes on gradually.
[/TD]
[TD]The pulsation dampener has worn out. [/TD]
[TD]Replace the dampener. Cost is around $175 and it is a very simple DIY project. Or around $600-800 if you have a shop do it.
[/TD]
[/TR]
</tbody>[/TABLE]