I have a 2016 Chrysler 300C with the 3.6 engine. I developed on oil leak behind the drivers side rear tire, I assumed it was a leaking shock. I removed the tire and the shock was totally dry. However, I noticed a small diameter rubber hose with a removable cap that ran parallel (vertical) with the rubber gas line, that is the source of the leak. The oil was very clear and heavier than engine oil. I called my local Mopar dealership and spoke with the service manager and a technician, neither of them knew anything about this small diameter rubber hose. I took a picture and sent it to a friend that has worked on newer Mopars for years at a dealership in Indiana and he didn’t know what it is or what it’s connected to. Any help is appreciated.

Gramps .... does this hose/line have anything to do with an “ active suspension” ? ... is there a FCA dealer close to you that can give you a no-charge repair quote ?

I’ll tell you this .... I’m not really super impressed with some of these so called service managers that I’ve talked with locally !!

There’s more true and actual hands on knowledge HERE !

Any chance its a vent for the rear diff ?
Im not familiar with the new ones. I Left the dealership nearly 10 years ago now ( wow time flies )

I’m thinking this. It definately looks like a vent hose, and the only common vents in that vicinity are the fuel tank and the diff. The diff shouldn’t be dripping more than a drop though....

Most gear oil has a pretty distinctive smell too. Have you gave it a sniff?

That's the rear axle vent.

I’m not sure about an active suspension vent. I don’t think it’s a vent line since it faces down and has a cap. But thanks for your input.

It doesn’t smell like the old 90 weight rear end lube. It really doesn’t have any smell.

I located the differential vent on top of the housing, just a very short section of hose with a plastic vent. I couldn’t feel any other hoses in the area. Since I don’t have a lift it’s hard to see everything under the vehicle. Thanks for your input.

Is this line in your picture located right next to the fuel tank filler tube?

I know the OP said “heavier than engine oil” but could that be the drain hose for the fuel filler cap area?

He said it didn't smell like gear oil, I imigine if it smelled like gas he'd notice that?

If you are responding to my post, be aware the drain surrounding the fuel cap also drains water....from rain and car wash etc.

Is this car a convertible? Paul

Yes, line runs next to filler tube.

Chrysler 300 doesn’t have any convertibles.

I put some gas in a squeeze bottle and poured/squeezed it in the overflow hole to see if it drained thru this hose, it didn’t. Remember, this hose has a removable cap but isn’t shown in the picture. Can’t figure why the Chrysler engineers designed a capped drain hose if it isn’t intended to drain anything. BTW, the cap was split which allowed this fluid to drain. I’m guessing there was about 8 ounces on my floor.

Can't answer why there is oil. Behind the plastic fender liner I believe there are fuel vapor containment components for emissions. It could be a service port for test equipment hence the cap.. Just a guess. I also thought of what has been mentioned about a filler neck water drain. Looks like a trip to a dealer to see if they can advise once seen. Has the car ever been worked on or wrecked in that area?

No, we bought the car new. Never wrecked or serviced by anyone other than one dealer oil change since new. I do everything myself. I’ll probably take the picture to the dealership to avoid a charge for a diagnosis.