[sarrac]

I have the strangest thing happening as of yesterday. I found myself stuck in my drive way, due to heavy rain, and attempted to switch to 4wd to get myself out.
but i remained stuck andit seemed as though my 4wd was not engaging.
My truck is a 99 F350 crew duely diesel 7.3 PST with the dial on the dash, 2W, 4W high and 4W low.
it took me sometime to get out and when i did i drove around trying to engage my 4w doing whatever i could think of. backing up, putting it in neutral ect... the strange thing is, the only thing that changed was that while my air was on, the venting would switch from dash vent to the Defrost vents. when i turn it back to 2W drive it goes back to the dash vents ( although it takes about a minute to go back)
i know this sounds crazy but ive tested it about 30 times. in each case my 4w does not engage but my vent configuration does.

does ANYONE have any ideas about this?

 

[Ford_Forgotton]

Common problem, you have a vacuum leak. Typically its the vacuum lines going into the front axle that break away and cause you to lose 4x4. Vacuum actuated hubs, remember?

Should be a simple fix.

 

[RedPony]

I have the same problem . Just waiting to take it to the dealership

 

[sarrac]

common thing, thats funny because its so bizaar. is it easy to fix/spot? or do i need to take it to dealer?
im guessing it would be fairly easy to fix the problem for me is knowing where to look, vacuum hoses is one of my biggest enemies because i have a hard time telling where the leaks are ( hard of hearing)
if you can, or if its possible, to give me an idea where to look or where it normaly breaks away id appreciate it.

ps. what else would this vacuum leak affect. engine runability? or any other componants?

 

[markbrown47]

Look behind both tires. You will see the brake lines and if you have 4 wheek antilock brakes you will see the wires for that. There is another line going to the hubs, that is the one. Check it at the hubs if it is dryrotted then cut about an inch or two off and reconnect. Problem fixed. Also if that is not it then check under the glove box, you will see two vacuum hoses, one black and one white, sometimes this will get disconnedted.

Mark Brown

 

[Wayne B]

[ QUOTE ]
Check it at the hubs if it is dryrotted then cut about an inch or two off and reconnect. Problem fixed.

[/ QUOTE ]

Do it right and REPLACE the vacuum line for about $2.00 ea.

Wayne B

 

[anchoryanker]

same prob here, definite vacuum leak.