Where does this vacuum line from booster terminate?

[drankinatty]

All,

Thoroughly enjoyed the [check charging system](https://www.expeditionforum.com/threads/check-charging-system-frustrating-issue.27924/) thread and it ended up leading to finding the GENCOM and GENMON wires frayed and broken about 2" back from the connector where it plugs into the harness about a foot in front of the PCM. Great discussion.

I have a lost vacuum line. Honestly, it's probably been that way for a long time. Likely since the last transmission rebuild. What prompted this find was I just finished the oil pump, timing chains, phasers, etc. where I had removed everything on the passenger side back to the firewall to get the valve cover off. (chains and phasers made it 254K miles before the chain guides disintegrated) During disassembly, I noticed the vacuum line (the line that runs from the booster, up over the back of the engine, is anchored to the back of the air-plenum on the passenger side with a clip, and then disappears over behind the PCM somewhere -- photos below). I thought I'd deal with it during reassembly, but reassembling everything, I still couldn't determine where in the heck that line terminates. Motor runs so smooth and quiet now, I could actually hear the vacuum leak instead of chain slap in the front cover.

The line and where it anchors to the plenum (dog-house, air-box, whatever the air intake is called) is shown in the first attachment, and where it originates on the brake booster is shown in the second photo. I've tried to highlight the line and anchor in yellow to distinguish it - but with limited success. I've searched the charm diagrams to try and find the diagram that shows the routing and connection, but I've had no luck. Does anybody know where line connects (somewhere near the passenger side firewall)? Currently I've just stuck a bolt in it to stop the leak.

Any help would be greatly appreciated.

 

[Gary Waugh]

I have an 08 and just went to see where that line goes, but apparently the 08 doesn’t have a vaccum line running across the firewall, I don’t even have the attachment on the brake booster as in your second picture, so am unable to help. Hope someone can.

 

[drankinatty]

Gary, thank you for checking. The mystery continues. The hardest part is just finding a good diagram for '05 so I can look it up. Worst case I'll call ford service and see if I can find a human that can look it up there ... but that presumes a knowledgeable human on the other end. That's getting tougher to find today.

 

[whtbronco]

I'm lookin', but I don't recall ever seeing a vacuum line there on any Gen 2 Expedition. My initial thought is that it is not factory.

 

[drankinatty]

Oh, it's factory. This expediton is 100% stock. Had it since it was new. It is the Eddie Bauer 4WD model - which likely makes the difference. It has the dual-automagic-climate control - which other than replacing the blend-door motor over the passenger side rear wheel well - still blows as cold as it did in 2005.

It is a 3/16 or 1/4 inch ID hose - a big one. At first when I looked at the free end, I thought it was just a breather for the front differential that was missing its cap. But then when I looked and saw it coming from the brake booster, there was no question. At first I just threw a plastic bag I had (I bagged and index carded all sets of bolt for the timing chain/phaser job). It pulls enough vacuum to suck the first 1/2 inch of the sandwich bag into the hose.

So it has to go somewhere. But all the smaller vacuum lines and connections below the PCM are all together and there isn't any "T" or the like not connected. The line to the reservoir on the back of the battery-box is connected -- so I'm at a loss.

I have a sneaking suspicion that there is some nipple somewhere either on the firewall behind the block or further over by the PCM that you can't see that's missing a hose - but even with a trouble-light and contorting myself into positions a person nearing 60 should never do, I still can't find it

 

[AWAR]

My 2wd 06 Navigator has that 1/4” vacuum line. It runs from the brake booster to the vacuum reservoir behind the battery tray. My 4wd 06 Expedition does not have that same line.

 

[drankinatty]

Ah Hah! So there is some entire section of line missing from the line coming from the reservoir behind the battery box to that line! The connection to the reservoir is there, it's a spongy (in need of replacing) connector going into a hard plastic line. (there are about 4 hard plastic lines of varying length that route below the PCM in various directions)

When I had the PCM, mounting plate and battery box out and was putting everything back together, I checked all connections (only 1 had been undone for the valve cover removal). It was reconnected, and I gave a careful look, but never found anything to plug the 1/4 line into. (there is a hard splice connector that is about 1/8" right at the PCM which is the only one I disconnected -- and the connection to the reservoir when removing the battery box)

I'm replacing the battery anyway tomorrow. It's 5 years 2 months old - and no longer spins the crank lickety-split, but shows ~ 12.43 - 12.45 V when fully charged, about 1/2 capacity. I'll pull the battery box again and trace the hard-line back from the reservoir and see if I can find the phantom connector.

Thank you, and thank you for your photos. Your battery mounts 90 degrees from mine. Mine is oriented against the passenger fender with the (-) by the PCM and the (+) toward the upper radiator hose. The reservoir and the lines to it are only visible when the battery box is removed. Now I have a defined rabbit-trail to go down!

Will report back, and with photos if I strike out and am back with hat in hand...

 

[whtbronco]

Looks like AWAR nailed it. That is another difference in the 2003/2004 to 2005/2006 Expedition. Mine is a 2004 Eddie Bauer and the vacuum reservoir is behind the battery, but the hose to it does not come from the brake booster like y'alls does.

 

[drankinatty]

Mystery Solved!

Thank you AWAR! Here is where the missing line connects - below the PCM. The line with splice connector is highlighted in red. You can just see the splice connector below and to the left of the 15 (or so) wire connector that feeds into the PCM connectors:



I now see why it was missed. During reassembly, after the valve cover went on (by the grace of god with the gasket still in place) the next job was connecting the vacuum lines. At that time all the wire bundles feeding into the PCM were tied back against the passenger fender. You can see what happens to that line when you pull all the PCM bundles to the left in the picture. (which is likely how that connector was pulled apart in the first place - it wasn't one I disconnected). The ground strap for the negative battery terminal was disconnected from the firewall, allowing the PCM bundles to move about a foot out of the way (thankfully).

Long story short, when the PCM bracket and PCM was installed and all the PCM connectors untied from the passenger fender - that line was buried below the PCM. I should have caught it, but I climbed all over looking for it and it was nowhere to be found.

With AWAR's phota and taking the battery-box back out and tracing backwards from the reservoir I was able to find the connector. Pulling the PCM connectors and moving the bundles to the right gives just enough room to get under the PCM to join the lines. (I had to check connectivity on the E67 pin anyway for a P0010 pinpoint diagnostic step HK7 - perfect connectivity between the bank 1 VCT connector and PCM harness end - that's the final phantom mystery to solve another day)

Thanks to all, the motor runs so smooth and quietly you could balance a dime on the air filter housing. Definitely recommend the Mellings 340HV oil pump if you are doing a timing chain/phaser job. Full 30 psi at hot idle (12 psi over stock). More than enough to keep the roller-followers, VCT solenoids and phasers well oiled and quite. 254K and running like a sewing machine!

 

[AWAR]

Anytime, happy to help.

 

[Fastcar]

Nicely done gentlemen!