Dinkyboy

Please see the attached pictures of my 2003 SL55 AMG. This is at the ride height button showing single red light as ON. Does it look abnormally high to you. The front height is fine. It is the rear that seems to be abnormally high. I am scared to take the height any higher by pressing the button again and having both the lights ON on the ride height switch.

Could the rear accumulator be the culprit? She rides pretty stiff at the rear and leaves the road quite easily on bumps. Also the rear tyres land hard with a thump when taking on a bump at slight higher speed.

my garage tells me that i need to change all the 4 accumulators. There is nothing showing up on star. I can understand to change the rear accumulator (in case it is found to be faulty) but why change all 4 is not clear to me.

thanks for the help in advance.

bobterry99

The accumulators should not affect the ride height.

A symptom of a failed accumulator is a momentary warning message in the instrument cluster when hitting a bump in the road.

Star Diagnosis can test the accumulators in a matter of a few minutes. The menu item for the test is somewhat hidden with my 2008-vintage software. Within the ABC menu I go to Troubleshooting by means of complaints or symptoms > Handling characteristics > Vehicle damping too soft or spongy handling characteristics > Pressure change during pressure release.

According to my software a failed accumulator will cause a soft ride -- not hard -- though this is contrary to what some owners report on the forums. My software states that a hard ride is caused by a faulty acceleration signal from a sensor.

I see no reason for you to fear pressing the ride height switch.

One of those pictures looks a little high to me. You can correct for it with a level calibration with Star Diagnosis.

Hary Gahtoe

Be proactive. Ask your Indie what the SDS errors showed. Even a MB dealer tech can miss a cue that another mechanic would find obvious.
Replacing all the Accumulators is solution IF suspension goes limp but not necessarily does that rule out some pressure loss conditions.

My question would be why would you replace parts that present the opposite characteristics?
Nothing can be absolute when asking questions online but from what little you describe symptoms are consistent to a stuck valve block. Crap gets stuck in the valves not allowing pressure to decrease to correct ride height.
A question (which causes relates to all this) is when was the last time you had the ABC fluid changed and is it almost black and smell burnt?
If so a fix would be
1. A full hydraulic fluid flush 10L with 2 hydraulic filters. 1 for a flush. # 2 for after flush for cleaned out system.

2. Remove the rear Valve block. disassemble, clean and replace.
3. SDS Rodeo and a Hydraulic reservoir top up.

Anyways, a Full SDS ABC systems check will help pinpoint pressure loss or too high pressure values.
A smart tech should've known all this or was quite possibly looking for more labor and parts ($$$'s)

moretech

I agree with Hary on the system flush as a starter, see if you have some luck and flush out some contaminants. Otherwise it may be time to pull the block and clean it out. Are both wheels up on the rear? If so it may be some faulty signal to the block. I sort of doubt both leveling valves fail the same way (UP) at the very same time. moretech

carguyshu

on a 2003 your accumulators probably all do need replaced due to age as they are for the most part going to be toast after 10 years or 100k. This is not causing the problem you are describing, though. The problem is likely the valve block as other have mentioned. Also, with the age of your car the orings are likely done in them and the blocks should be rebuilt (jnash on the forum does this service and also has posts detailing how to do it for a few dollars with of orings). If you are going through all of the work on removing the rear valve block in an 03 (they dont have quick disconnect release hoses like the newer model years) you should pay the few extra dollars to get them rebuilt.

bobterry99- the reason a bad accumulator can cause a harsh ride is if the ABC system senses pressure is too low (due to the accumulators being bad) it will lock all of the valve blocks so that no fluid can go in or out as a safety measure. This will result in a lumber wagon like ride for the few seconds that the valves are locked until pressure is built back up. This condition will obviously also cause an ABC warning light.

carguyshu

also, if one accumulator is bad, then it won't be long until the rest are. The accumulators are there is basically make pressure consistent across the system and are rubber and nitrogen filled. That rubber over time will deteriorate due to age and they will stop working the way they should. If you have a valve block out, it is quite easy to replace the accumulator for that valve block, but again you should change them all out at the same time if one is bad.

bobterry99

You are correct that a low pressure condition will cause the valve block control and lock valves to close. However, with the valves closed the vehicle would not have the harsh ride that you expect, since the passive suspension components of an ABC-equipped car are extremely compliant. You can see this for yourself by grabbing hold of a vehicle at a wheel arch and pushing-down and pulling-up on the chassis. I know of no other vehicle with a suspension so soft.

The moment ABC deactivates going over a bump the valves will close and any hydraulic cylinder in motion will sharply decelerate, and perhaps that would be perceived as harshness. At any rate, owners also report harshness even when no ABC fault is present and the system is active, so the explanations offered on this thread would not apply to those circumstances.

dinkyboy1

My car has been at the authorised MB dealer for months now ( not their fault). The parts take ages to reach. I have installed following new parts (all original MB parts):

1. New Tandem Pump
2. All 4 new struts
3. Both new Valve blocks
4. New hoses

The only thing i did not change is the Accumulators. I do feel that she is high from the rear. Best i will post photos of the height of the car in all the three stages. Can someone please tell me what the right ride height should be in these positions for the front and rear of the car.

bobterry99

If you explore the section on the ABC suspension here I think you will quickly realize there are many components you have not replaced.

In my earlier reply to you I wrote that your car appears a little high. With the benefit of a closer look I would say "little" is an understatement, and it is peculiar to me that your shop does not correct this obvious abnormality. I suppose they lack the equipment to perform a level calibration or have no knowledge of it.

Dinkyboy

Most friends here have pointed to stuck valve blocks. However both the valve blocks are brand new. So very little chance of anything wrong there. The struts are brand new as well.
What else could be wrong please?

dinkyboy1

does anyone know of a procedure in star diagnostics which can check on the health of the accumulators and the pulsation dampners?

kbob999

I don't believe there is a test on the SDS. At this age they need to be replaced. 10 years and they are worn out.
The only test I know is to stick a pencil in. 1" in is good; any more than this is bad due to failed diaphragm.