Thanks -- appreciate it!
I did have scale on my heating tube, which I removed with vinegar when I had it out.
The other stuff I'm talking about is more like slimey flakes... I would have taken the tank out but it looked like kind of a PITA and I didn't want to risk breaking some old seal or something.
I'll try stirring the flakes up to suspend them in the fluid, then sucking the fluid out with a shop vac. If I repeat that a couple times hopefully that will take care of it.
So anybody have a clue on #3, the clear tubing? I looked on the Mercedes parts CD but it isn't shown separately.
1999 E320 Wagon