Keith Browning Posted August 4, 2005 Share Posted August 4, 2005 Looking for a vacuum leak in the pulse vacuum 4X4 system? Hook-up and crank-up the emissions smoke machine to the vacuum line at the regulator. You will find the leak! /forums/images/%%GRAEMLIN_URL%%/thumbup.gif Quote Link to comment Share on other sites More sharing options...
Mike Hutchins Posted August 5, 2005 Share Posted August 5, 2005 that is a very good idea who would have thought of it,(well I guess you did) Quote Link to comment Share on other sites More sharing options...
Keith Browning Posted August 13, 2005 Author Share Posted August 13, 2005 Yeah, we had a 250 in that has had a long history of 4X4 engagement problems. So I look to my tech and ask him just how many hubs will be thrown at this truck before someone realizes that the problem is not the hubs? We monitored the system vacuum while operating the switch on the lift. All was good, the pulse vacuum system was operating as it should and there was full vacuum. So we thought to put the smoker to it and look for a small leak at the hubs that may have been causing intermittent engagement probs. Son of a gun! The inner seal on the left side started wisping smoke. The point is, even though you have vacuum, do you have enough? On this vehicle, we had a small leak, just enough to cause a problem but not enough to be obvious. Quote Link to comment Share on other sites More sharing options...
STROKER_T Posted June 15, 2009 Share Posted June 15, 2009 I got one now,'06 F250 that the vent air flow switches to defrost only when 4 x 4 is switched on,and goes back to vent after a few minutes,have tried the smoke machine,which is an awesome invention ,maybe i'm not seein' it...but it seems like a vacuum issue. Also getting intermittent C1145 for r/f abs sensor,its been replaced,was wondering if the hub has an issue that relates to first mentioned,or its something to do with the rear axle carrier(tsb)? Anyone had something similiar? Probably shoulda started a new thread,sorry... Quote Link to comment Share on other sites More sharing options...
Keith Browning Posted June 15, 2009 Author Share Posted June 15, 2009 Sometimes it is probably best to add to an old topic... I have two things to add to this: first, when smoke testing, be sure to exercise things as best you can like rotating the driveshaft, rotating the wheels and turning the wheels from lock to lock while on the lift. Have a helper assist you. This will help find those little leaks that happen only with "certain" conditions. I also recommend taking a vacuum gage, and tee it into the air line going TO the axle just after the vacuum regulator. This way you can monitor the system operation and you can also check the system by doing a bleed down test - which is no a test you will find in the book - I have no specs but a solid system should hold vacuum for a reasonable amount of time before any bleed down is noticeable. Quote Link to comment Share on other sites More sharing options...
8WA Sman Posted January 30, 2020 Share Posted January 30, 2020 I had a 2014 SD with Auto hubs inop. Smoke test revealed cracked LF knuckle hose. Replace hose now smoke test passed unless I was rotating the wheel beraing(.010 in hg of flow) but vacuum test failed on both hubs. I couldn't even get 5" in hg while constantly pumping. So hooked up my brake bleeder and started spraying around listening for that sucking on an empty straw noise. I noticed when I sprayed around the Ford logo it would dry out quickly. So I put a piece of tape there and could see the vacuum making the logo more defined. Now with a hand pump the vacuum would hold then instantly drop when the tape was removed. 1 Quote Link to comment Share on other sites More sharing options...
jimmy57 Posted January 31, 2020 Share Posted January 31, 2020 Does this prove what so many have said? "Ford sucks". Seriously: I had non functioning hubs on one with good hub sealing and also found hub knob leaking. When the diagnosis was made the owner asked why the knobs didn't turn very far like on his older Bronco and admitted to cranking on them as they feel like they were not locked. The hubs were not marked up but he is stout man and I guess has some considerable hand strength. Quote Link to comment Share on other sites More sharing options...
batmantech Posted February 3, 2020 Share Posted February 3, 2020 Had a super duty last week. No hub engagement. When I turned the hub(turned very hard) It had a foamy substance that come right out of the "Ford" name on the hub Quote Link to comment Share on other sites More sharing options...
8WA Sman Posted April 18, 2020 Share Posted April 18, 2020 This is an update correction to the above post and hopefully everyone that read the original post will read the update so as to not mislead anyone. After dissecting 1 hub several weeks after installing the 2 new hublocks and not finding the diaphragm leaking I got the sinking feeling my diag and understanding of exactly how these hubs work was not 100% accurate. I made a test stand which lead me to suspect when this problem occurs(leak in the Ford logo) that the problem is actually with the orange O-ring.....Well I saved the 2nd hub and installed it on a truck today and my suspicions were correct. Thankfully both old hublocks had noisy center splines but my diag was still not 100% accurate. So it looks like I will be writing my own stimulus check to the owner..Edumacation ain't cheap Quote Link to comment Share on other sites More sharing options...
forddieseldoctor Posted April 19, 2020 Share Posted April 19, 2020 Good to know. Quote Link to comment Share on other sites More sharing options...
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