The car in question is a facelift, 2014 E550 sedan.

Can anyone tell me what fluid is blue-green and oily? No strong smell. Definitely doesn't look like engine oil or gear oil.

What color is 722.9 transmission fluid? Is it red like most ATF?

I found a small puddle of this stuff in the center of the parking spot, toward the front of the car. I'm thinking hydraulic fluid or something from the transmission or front differential. Does the car have steering hydraulics even though the system is described as electric power steering?

I will investigate further when I get the car back- currently it's at the detailers, which is why I took the time to clean the garage floor and found the puddle.

 

Electric assist power steering has no hydraulic fluid. Did you spill some windshield washer fluid when topping up by chance?

 

Windshield washer fluid came to my mind first too. Could have a leak in the pump seal and dripping finds it’s way to the center of the car.

 

chances are this will match your coolant fluid. Find your leak... hairline crack in tank?

 

It's definitely not windshield washer fluid- that's not oily in consistency, nor is coolant. Both are watery. I think my coolant is pink.

 

Is PINK coolant compatible? I thought the approved chemistry was either Yellow or Blue

 

My car is at a detailer's shop right now, so I can't look at it until I get it back. I will put it up on ramps and poke around underneath to see if I can find what's leaking or not. I've already made an appointment at the local dealer to take a look at it in case I can't find it and fix it myself.

The secondary coolant tank near the firewall (the really tiny one) has pink coolant in it, that I'm sure about. I don't know if the main circuit has different coolant or not.

My old W204 had blue coolant, like my old Volvo and my BMW.

Coolant isn't "oily" in feel, though. It's a bit slicker than water, but maybe I'm overthinking this. Would a radiator leak get caught by the belly pan and end up much further back? Any ideas on what typically fails in the cooling system? This car only has 50k miles on it.

 

https://www.mercedesbenzofdanbury.co...id-danbury-ct/

I am not sure what is the difference between "oily" and "slicker"y for you, but while changing the radiator overflow reservoir (W211), I got coolant on my hands and the wrenches/ratchet slipped from my hand while picking them up, is that slippery enough to be called oily?

 

Coolant is oily in feel @ least the MB blue stuff if it's not mixed with water.

 

I will update this thread tomorrow- I'll have the car back by then.

So if it's coolant, which, after talking to a few people and reading here, it probably is coolant- then where are the typical points of failure? Judging by where the pool was, it was by the firewall, pretty far back from the radiator, and dead center.

Thanks for everyone's help and for putting up with my stupidity!

 

Could be the water pump leak

 

How much coolant do you lose over what time period? Official MB coolant would be Blue for your year but VIN dictates all. 2014 is a transition year. There is an inflow through the firewall from engine to interior. There is a hose-type part that is susceptible to failure with many heat cycles. This 'leak' may condensate on the firewall and drip down to under the center of the vehicle. Reservoir area and water pump area should also be investigated. I tied paper towels around the reservoir hoses to diagnose in my previous case. I am currently investigating my firewall, but have not gained complete access yet. Whatever your case, take a few pictures and share when you can.