Vacuum Line Behind Battery
06-13-2013, 01:29 AM
#11
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Does your truck have vacuum actuated 4x4? If it does, that line that is open is the vent line going down to the 4x4 actuator. its paired with a vacuum line from the 4x4 vacuum solenoid. As far as the codes, check that the vacuum check valves are still good. The help maintain a vacuum in the 4x4 system under acceleration. Perhaps your system is leaking somewhere too. Go get one of those brake bleeder/vacuum check kits and go through the system yourself.
Last edited by lljlehr; 06-13-2013 at 01:34 AM.
11-19-2016, 07:56 PM
#13
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Maybe this is a little late, but I found out where that out what's up with that mystical black "vacuum " line goes. I was stumped with that same issue trying to find a vac leak my self, that's how I stumbled onto this forum thread.
If you trace where the other end of that line goes, you will find it goes directly to the front differential just above the vacuum actuator that engages the diff for 4x4. It's a 3/8" hose at the diff , changes to the lil 1/16" up on the fire wall. It's just the open end of the breather hose from the diff. It's not supposed to be connected to anything! Mine actually had a slight down turn to keep water out.
I did have to repair both the other blue and white vac lines that run along side it to control that front diff, they were completely toast!
Maybe u already figured this out, but if not, maybe it helps. 😉👍
If you trace where the other end of that line goes, you will find it goes directly to the front differential just above the vacuum actuator that engages the diff for 4x4. It's a 3/8" hose at the diff , changes to the lil 1/16" up on the fire wall. It's just the open end of the breather hose from the diff. It's not supposed to be connected to anything! Mine actually had a slight down turn to keep water out.
I did have to repair both the other blue and white vac lines that run along side it to control that front diff, they were completely toast!
Maybe u already figured this out, but if not, maybe it helps. 😉👍
11-20-2016, 10:24 PM
#14
Thanks for the help! After all these years, I never did figure it out. The 4wd always engaged, and I eventually fixed my lean codes so I quit trying to figure it out. The fact that it's a breather tube makes lots of sense.
11-21-2016, 09:38 AM
#15
Does your truck have vacuum actuated 4x4? If it does, that line that is open is the vent line going down to the 4x4 actuator. its paired with a vacuum line from the 4x4 vacuum solenoid. As far as the codes, check that the vacuum check valves are still good. The help maintain a vacuum in the 4x4 system under acceleration. Perhaps your system is leaking somewhere too. Go get one of those brake bleeder/vacuum check kits and go through the system yourself.
11-21-2016, 04:05 PM
#16
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Lean codes 171,174
So, just curious, what was your fix for the lean codes? I been trying to track this down for weeks now. Mass air flow sensor, 02 sensors, fuel pump, change out deteriorated vac lines. All needed fixing, but looks like still have vac leak, long term fuel trim levels are still 28-29% steady. Any one els have input on this one???? I'm thinking bout looking over the PVC line good n close right now.
10-02-2017, 07:15 PM
#17
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Vacuum line behind battery
The vacuum reservoir is part of the battery box and those vacuum lines are for your hvac plenum functions, vent/defrost/floor.
Turn the air on and find an open stretch of road and floor it, you will experience air flow changes. It will also cause lean codes.
Just repair them and no worries.
.
Turn the air on and find an open stretch of road and floor it, you will experience air flow changes. It will also cause lean codes.
Just repair them and no worries.
.
02-12-2020, 03:49 PM
#18
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Vac line. beside vattery
That does make perfect sense. My AC has been acting up and been very unwilling to shoot out of anything other than the defrost vents. The problem is, I have no idea where this vac line goes to. Any ideas? The hose is in the middle of the picture, which is on the passenger side of the truck looking towards the firewall (battery and tray removed). Thanks for any help.
Mine had a hole in it...dry rotted and brittle in part of line. Then go to find it broke off inside the rubber coupling, so i took it off of the blue thing in the upper right of the picture. took a fuse tester and pushed the broken part out, then reattached , tried putting clear tape (not the tape one uses on things like this) on part of hose with hole for temporary measures. Couldnt do a lot with battery in my way, and I'm at work. Thanks to this post, because I know how to fix it and don't have to panic seeing doesn't directly affect the engine. I
hope not. I'm not really a mechanic, but know a few things. Wondered why my heat cut off and on in the vents.
Vac line going into blue valve. Pass. side, left of battery.. 2003 Ford F150 5.4 Triton V8. My not so great fix with with Scotch tape. Still sucking a bit if I mess with line.