Hi. Brand new here so I hope I'm in the right place. Need help I.D.ing what should be something relatively simple. With so many options and wordings in an ocean of information, I can not just google. I have a 2003 F150 XL 4.6 2WD with rear disk. While on a hot remote desert highway in very hilly British Columbia, after a roadside break, I noticed a line dangling from underneath. I got under there I found it was a rubber hose coming off the rear brake tee. There is of course the fluid source line in then the two lines going off to each wheel. The fourth line of concern was intact at the fitting, loose at the other end. There is a plastic fitting at the non tee end. This is what I think but please tell me if I'm wrong and what the function of this line is. I am not certain but I think the plastic insert fitting (loose end) is meant to be open.(something to do with vent or pressure equalizing?) It looks like there are tabs (broken off) that hold it in place in a hole in the frame. I can not see anywhere else this would go. I just tucked it up and kept going with no notice in driving. Any input greatly appreciated. [IMG][/IMG]
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Great pictures. My 2000 F-150 has the same hose. It is infact called a vent even though the brake system is a closed system. Your picture #2 shows the factory location just to the left and below on the picture. There is a cable with a U shaped clip that the hose just snaps into.. If it doesn't stay there just use a zip tie.

 

Great, thanks. So it is just open ended. Good thing because that is what I told my girlfriend at the time. She was a little freaked out.

 

Its a vent hose for your rear differential. It has nothing to do with your brakes other than that the nipple it is connected to also is the bolt (perse') that holds that tee to your axle houseing.
Nothing to worry about.

 

Its the vent hose for the rear axle it does indeed go into the hole in the cross member that is to keep it up high and dry

 

Thanks everyone. That satisfies my question.