Calling all experts - ASD help please
 

So far I have managed to stump the local MB know-it-all and the dealerships on this one...

I have a 92 300D 2.5 with ASD ( locking differential ). There is a fluid management unit of some sort that sits infront of the passenger rear wheel. It makes a click-click sound every few seconds. Over the past 2k miles is has been getting loader. There is a high pressure line that runs from the power steering reservoir over the radiator which pulsates with the clicking. What could be the problem? Any thoughts are appreciated

Have had that very problem since I bought my car 4 years ago.
Pulling my hair to find the cause.
Most likely it is the Hydraulic Unit charge valve, or the pressure sphere. If i disconnect the return line called T at the fluid recevoir, I can see the fluid moving back and forth with the sound, due to some pressure pulse in the unit.

Did you ever solve the mystery?

/Viggo

I think this is caused by a faulty pressure valve, the pulse is the overpressure checkvalve opening.

I would start with the accumulator sphere. It is normal for the pressure release valve to open but without the sphere to dampen it you get the hard pulsation.