# Ford vacuum leak in 4x4 **URL:** \ **Category:** Maintenance/Repairs\ **Tags:** f350, ford\ **Created:** [December 21, 2011, 10:33pm UTC](https://community.cartalk.com/t/ford-vacuum-leak-in-4x4/70085 "2011-12-21T22:33:03Z")\ **Posts on this page:** 8\ **Page:** 1
**Author:** ![notamechanicHELP](https://avatars.discourse-cdn.com/v4/letter/n/e274bd/32.png) [@notamechanicHELP](https://community.cartalk.com/u/notamechanicHELP)\ **Post date:** [December 21, 2011, 10:33pm UTC](https://community.cartalk.com/t/ford-vacuum-leak-in-4x4/70085/1 "2011-12-21T22:33:03Z")
my ford’s 4x4 will work if I manually lock in the hubs. If i use the auto option it will not engage. I can feel the rear end diff lock when I put it in 4-low so I know the switch is working. I think it is a vacuum actuated system. Any suggestion or helpful hints on how find hte leak or diagnose the problem? TIA!!! ---
**Author:** ![MikeInNH](https://avatars.discourse-cdn.com/v4/letter/m/a587f6/32.png) [@MikeInNH](https://community.cartalk.com/u/MikeInNH)\ **Post date:** [December 21, 2011, 10:53pm UTC](https://community.cartalk.com/t/ford-vacuum-leak-in-4x4/70085/2 "2011-12-21T22:53:21Z")
Never seen that setup before. Either the hubs were automatic…or they were manual. Never seen the hubs that have both. Last truck I owned that had this type of setup was my GMC S-15 (actually made by Chryco New Process Gear). There was a vacuum activated diaphragm. If there was a vacuum this would prevent the hubs from locking. The diaphragm sat in the fenderwell. ---
**Author:** ![ken\_green](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/ken_green/32/816_2.png) [@ken\_green](https://community.cartalk.com/u/ken_green)\ **Post date:** [December 22, 2011, 1:47am UTC](https://community.cartalk.com/t/ford-vacuum-leak-in-4x4/70085/3 "2011-12-22T01:47:45Z")
Complete info in your initial post is imperetive. like… the… Year ?? There are many places for vacuum to leak. Vacuum solenoid. vacuum tubes/lines, which have a check valve. Hub seals and o-rings. On a popularity scale we sell more hub seals & orings than the others. ---
**Author:** ![notamechanicHELP](https://avatars.discourse-cdn.com/v4/letter/n/e274bd/32.png) [@notamechanicHELP](https://community.cartalk.com/u/notamechanicHELP)\ **Post date:** [December 22, 2011, 2:12am UTC](https://community.cartalk.com/t/ford-vacuum-leak-in-4x4/70085/4 "2011-12-22T02:12:05Z")
sorry – 2000 ford 350 90K v-10 - i have replaced the front right Hub. ---
**Author:** ![ken\_green](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/ken_green/32/816_2.png) [@ken\_green](https://community.cartalk.com/u/ken_green)\ **Post date:** [December 22, 2011, 3:24am UTC](https://community.cartalk.com/t/ford-vacuum-leak-in-4x4/70085/5 "2011-12-22T03:24:58Z")
By HUB , do you mean… The hub and bearing or the 4x4 locking hub ? Vacuum needs to be trapped within the hub and bearing area. The big grease seal AND the outer yellow o-ring are responsible for that in this area. There is a vacuum reservoir on the right fender with a check valve, a vacuum solenoid on the firewall, and lines between that all need checked for leaks. ---
**Author:** ![notamechanicHELP](https://avatars.discourse-cdn.com/v4/letter/n/e274bd/32.png) [@notamechanicHELP](https://community.cartalk.com/u/notamechanicHELP)\ **Post date:** [December 22, 2011, 4:09am UTC](https://community.cartalk.com/t/ford-vacuum-leak-in-4x4/70085/6 "2011-12-22T04:09:37Z")
any trick for checking these lines? I am asking in the most basic of descriptions, how does one go about checking for leaks? ---
**Author:** ![notamechanicHELP](https://avatars.discourse-cdn.com/v4/letter/n/e274bd/32.png) [@notamechanicHELP](https://community.cartalk.com/u/notamechanicHELP)\ **Post date:** [December 22, 2011, 4:10am UTC](https://community.cartalk.com/t/ford-vacuum-leak-in-4x4/70085/7 "2011-12-22T04:10:04Z")
crap and this the 4x4 locking hub… ---
**Author:** ![Newpoint95](https://avatars.discourse-cdn.com/v4/letter/n/bbce88/32.png) [@Newpoint95](https://community.cartalk.com/u/Newpoint95)\ **Post date:** [December 26, 2011, 7:01am UTC](https://community.cartalk.com/t/ford-vacuum-leak-in-4x4/70085/8 "2011-12-26T07:01:18Z")
I use a hand held vaccume pump that has a gauge on it. You can attach it to each hub and apply vaccume. It should hold, if it drops you have a leak at the hub. If it checks out connect the pump to the main line in the engine compartment and test the entire system. Hope it helps.