I recently replace PS fluid and filter. Both parts and fluid is original MB. I want to know why the fluid turn dark so quickly as compare to fresh one in bottle? Help

The PS (or ATX) fluid is highly detergent and will clean out residue that built up before your flushed your steering system. It is great for cleaning greasy parts and bolts

If it bothers you, let it run for a few weeks then flush again.

If you siphoned the reservoir with a turkey baster and refilled, you ended up replacing maybe just half of the fluid. A lot of PS systems on MBs hold a good deal more than a qt. So a qt. of new blended with approx. one qt. of old.

You need to pull the return line, point it downward into a pan and have someone start the car and turn the steering wheel back and forth. While this is going on, you're up front pouring fresh fluid into the reservoir as it runs out the return line.

Try this next time. It's the only way to thoroughly flush out the PS fluid.

__________________
Mike Murrell
1991 300-SEL - Model 126
M103 - SOHC
"Fräulein"