Offhand, I don't know if there is a testing procedure for determining the condition of the accumulators. From my recent experience, I would say if your accumulators are more than 10 years old, replace them.

I based the decision to replace mine on the following:

1) The ride was harsh. You could feel every expansion joint and bump in the road. Even minor bumps in the road would literally move you up and down in the seat.

2) The ride quality of my wagon was SIGNIFICANTLY different from the W123 sedan that also I own. Somehow, it seemed to me that the engineers at Mercedes-Benz™ would not permit this sort of difference.

From those two conditions, plus an understanding of the way the rear suspension works in these cars, I deduced that collpased accumulators (no gas space left in the bad accumulators would allow no additional springing by compressing the gas) would be the most likely cause of the harsh ride.

It was an educated guess that turned out right.

Some other hydropneumatic suspension scenarios:
An excessively springy (no damping) ride would be indicative of bad struts or no fluid in the system (a leak).

Failure for the SLS to maintain proper ride height would be: 1) no fluid in system, 2) failed or sticking position sensing valve, 3) broken or loose linkage from sway bar to position valve, 4) broken sway bar links at wheel, 5) failed SLS pump.

Based on the above, you'll see that it's really pretty simple to diagnose these systems. IMO, and considering what they do, they have to be one of the most trouble-free systems on the car and well worth putting money into for a proper repair.

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Never a dull moment at Berry Hill Farm.