Ive got an 08 5.4L, and today I noticed a vacuum line that comes from the caliper into the engine compartment on the drivers side. It just sticks up going nowhere. Its attached to another one with a clip, and I can't find where its supposed to go. If it goes anywhere. Can you guys see if your trucks have the same thing? Its directly under the intake tube next to the brake lines coming out of the master cylinder.

 

I think that line is for 4x4 operation. You dont specify if you have a 4x4 or not.

 

I do have 4wd, I wish I could post pics.

 

If it is a very thin rigid black plastic line, then it is the 4X4 vacuum line which probably goes to a connection between the battery and the firewall. With it disconnected your front hubs may be engaged all the time you are driving. It could also allow water into the system which will cause big problems. Look around behind the battery and see if you can locate a connector which has an open port on it. The 4X4 vacuum solenoid is mounted on the firewall and has similar black plastic lines run to it. Mine came unplugged not long after I bought the truck and I discovered it and put it back where it belonged. Hope you get it working. Good luck.

 

Here are some pics

 

That appears to be on the driver's side of the engine bay. If it originates at the knuckle it is probably the vacuum actuator line for the front hub. There is also a vent tube for the front differential that comes up into the engine bay but it is a larger diameter rubber tube and it needs to remain open for the diff to breathe.

 

I have exactly the same thing on my 2005 4x4. its been driving me crazy looking for the other connection. Can you let me know if you have any luck, Thanks

 

Those are the vent tubes for the IWEs on each front wheel.

 

Yes they are supposed to be left open without a connection.