I was inspecting the rear brake hose on my 96 E350 and I noticed there are actually two hoses along side each other. One of them was cracked wide open, but there was no sign of any oil coming out of it. This second hose that is split open runs from the terminating block up to a strange looking plastic fitting. It doesn't seem to do anything or go anywhere, and there is no mention of it or diagram showing it in the factory shop manuals.
Does anyone know what this extra hose is and what it's supposed to do?
Thanks

 

I believe you are talking about the rear axle vent.

 

I agree. Differential vent. As the inside heats up, pressure vents out. If you plan to do a lot of river crossings, you may want to extend it to the gas filling cap.

 

You mean that block the hoses are attached to actually has a hole in it that goes into the axle?

 

There is a junction block where the rubber line from the master cylinder travels to the axle, splitting it to two steel lines running to each wheel, it is secured to the axle tube by a hollow bolt, with a hose that travels up to the frame, which is the vent, I've replaced them with longer lines running higher up, capping with a filter to insure no trash or bugs enter, spiders and wasps like to plug it with a nest.

 

At first I thought it was a burst brake line. Just a lousy vent. Ha. Thanks guys for solving the mystery.