Can anyone tell me what this part is that is leaking?
 

The leak is coming from a cylindrical part at the front left (driver side) of the car, fairly close to the bumper -- well ahead of the wheel.

Photos were taken from the driver side, pointing to the passenger side.

Thanks.

Looks like a suspension bushing leak to me.

Yes, it definitely looks like a suspension bushing, but those are not filled with any fluid.

Yes, however, something else may be dripping on to it. Definitely a suspension bushing.

I showed it to someone who thought it was power steering fluid dripping on the suspension bushing. The only thing is, the PS fluid that I've seen is always red, and this is very much black like ink.

In any case I need to go to either my local mechanic or the dealer and have them check it out.

Yes, they used to be filled with fluid. Replace both lower control arms. The new ones are not fluid filled. You will get a noticeable better feel and ride comfort when you replace these. Replace both sides. This is an easy part to replace.
They were fluid filled because it soaked up road noise and bumps better.

Bushings filled with fluid, huh? Wow, you learn something new every day!

That's what I thought too. Mine leaked soon after I purchased it. I let it go for years before it started to make a 'clunk' sound when going over bumps. New ones are not fluid filled.

Well thats a new one on me as well .

Are you sure the 4matics were fluid filled? The arms I removed didn't look like they were and my records said no prior replacement so they were original.

I just went through this job and you have to replace the entire arm if the bushing that the strut bolts through looks worn at all ($450/side). If the strut bushing is OK, then its $140 for the bushings/side and you'll need to have them pressed in.

I'd check for something else. Power steering fluid is black when its used up. I just replaced my PS fluid and it was black. New is green.

It was a while ago. Mine is an 03 RWD. don't know anything about this part in any other year or the 4matic models. The fluid that came out of mine looked blue though. I've never seen a replacement part anywhere that said fluid filled.
I replaced the entire arm(s) because it came with bushings on both ends of the control arm. It was going to cost about $50 to press the old bushing out and new ones in.

I took it my local mechanic and he replaced both front lower control arms and both ball joints.
Total parts $1311, total labor $584 (including a 4-wheel alignment). So, with sales tax, it was over $2000!

dang! if your had air, impact gun, pry bar, and 21/22 mm socket and wrench you coulda saved yourself the labor! Bet shes riding nice now tho!

I would have said it was the motor mounts. I am surprised that replacing the control arms and ball joints would fix this.

The motor mounts are oil filled and after some years they will fail.