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4x4 vacuum leak

5K views 13 replies 5 participants last post by  Zmann 
#1 ·
i have a 2000 f350 . the 4x4 works great when i get out an manually lock in the hubs.. however when I have it in auto lock and turn the 4x4 switch on the dash it does not engage and takes my a/c and blows out the defrost. Any ideas?? I assume I have a vacuum leak but not sure where to start.
 
#2 ·
start by plugging off the vac tubes at the front wheels first guess would be the hub seals......
 
#4 ·
they can be a pain if you don't know what you are doing I would verify by plugging off one side at a time first.
 
#5 ·
If the leak is so big it causes your AC to switch to the defrost vents, I'm thinking you have a broken line. Look real close where each line goes to the knuckle. Dry rot will make the rubber porous. One of those hand held vacuum pumps would be helpful in finding the leak regardless of where it is.
 
#7 ·
the seal will leak enough to cause problems too!... all it takes is some one to do a balljoint with out pulling shaft to screw up seal enough to make it leak. If you ran in 4wd in rain or snow, with a leaky seal, brearing is probably on its way out too. thats why I put in warn hub locks and did away with auto hubs. If your too lazy to get out and turn a couple knobs a quarter turn you probably should not have a 4wd because you should be in 4wd BEFORE you need it.
 
#9 ·
no... you will still need it to shift transfer case. the only thing it changes is you have to get out to lock hubs. The biggest difference is the vac. wont pull moisture in to hub bearings so they will last longer..
 
#13 ·
I have the same problem on my E99 7.3 F350, the hoses are completely gone, I have to manually engage them (which is difficult cause the lockouts are filled with all sorts of crap) and then flip the switch in the cab. I was talking to my dad and we are probably going to get new hubs (because our wheel bearings are wearing down) and get new lockouts and maybe a 4x4 vacuum if we need it. But we are probably replacing the lines with stainless steel hoses instead of those rubber ones. I will keep you updated when we do the job and let you know how it goes.
 
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