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All those vacuum connections under the Explorer upper manifold

John Griswold

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Joined
May 3, 2010
Messages
210
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Medford, NJ
This has been discussed in a few posts but every year manifold seems to have slightly different lines under the Explorer upper manifold. Mine is the 99. How many are required? Like the two running off the metal heater line to the front? The PCV is connected to two, one front and one back? Evap has one on the back? It been discussed removing the one on the drivers side that partially blocks the valve cover hole. Are these just pressed fit and can be worked out? How do you plug it? Lots of lines, lots of questions!
Thanks
 

JSmall

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Joined
Feb 18, 2004
Messages
3,223
On my 97 I’m only keeping the line for the fuel pressure regulator and PCV. The rest were removed, drilled, tapped and plugged
 

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hankjr

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i pulled out / drilled out all my metal tubes and tapped for NPT (96). i used adapters to inverted flare and bent steel tubing to get vacuum where i needed them. i think i only plugged one of the 3/8 holes and used everything else.

Hank
 

BroncoChicken

Sr. Member
Joined
Mar 29, 2015
Messages
356
We only used the PCV and the fuel pressure regulator. Pull the rest of the hard lines out and tap/plug them, or you can just cap them. Long term, it’s better to have them plugged. If you run a c4, which I know you aren’t, you need another for the vacuum modulator. My heater line didn’t have the in/out for the two lines that go to the front of the upper intake. You can just find a small heater hose and loop it to connect the two nipples on the heater line.

The PCV valve is only connected in the rear. The other PCV line should go from one of the valve covers (passenger side is easiest) to the intake, somewhere between the MAF and the throttle body. The ‘96 throttle body has the PCV connector built in, other years have a nipple on the air intake tube. I’m pretty sure you can’t connect both sides to the intake.
 

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DirtDonk

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As they pointed out John, it's not what year the Explorer manifold is, but what your engine and vehicle actually needs. Some only need two...

How are you running yours? Full Explorer EFI with coil packs and CAN-P circuit enabled?
Power brakes? Old transmission or 4r70w?

Sounds like you have the PCV correct. Although some just use the one tube and not both, I say two is better than one.
The PCV clean air return is not vacuum of course. But no breathers allowed for mass-air EFI. Needs to run from one valve cover to the intake fitting. NOT full vacuum. The valve gets vacuum, the return does not.

Fuel pressure regulator.
Brake booster if needed.
Trans modulator if needed.

The heater line fittings are for water to the throttle body to reduce icing in winter. Not vacuum.

The charcoal canister only gets vacuum if the Can-P circuit is enabled to control the solenoid valve. Otherwise it gets plumbed into the air tube area between the MAF and the TB.

Paul
 
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John Griswold

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May 3, 2010
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Loc.
Medford, NJ
Ok, going to be 4R70W trans so no modulator, hydro boost brakes so no booster, don't need the two from the heater lines, returnless EFI so no pressure regulator but a pressure damper, and PCV valve.
Help me out with the Can-P thing, not sure what that is. EFI Guy wired me for the evap purge solenoid which I am not installing right now. I don't have an evap vent at the tank right now but have the capability to add one later.

So I need:
One small line for the damper.
One or two large lines for the PCV.
One line capped off and accessible for possible evap system later. What is the evap, large
or small?

And one last clarification. From the driver side valve cover hole (Bronco Script covers) gets the hollowed out PCV valve as a 90 and goes to the inlet tube fitting between the MAF and the throttle body. This is the PCV clean return. Think I got it?
 

DirtDonk

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Help me out with the Can-P thing, not sure what that is.

Stands for "canister purge" and is just what you talk about below, the evap solenoid.
The point is that, unlike early systems that do NOT use vacuum, this one does use full vacuum from the intake. But with the solenoid controlled by the computer, that's not an issue.

EFI Guy wired me for the evap purge solenoid which I am not installing right now.

Great! You're all set then.
You only use full vacuum with the evap system when this control circuit is active.

I don't have an evap vent at the tank right now but have the capability to add one later.

Sounds good. It usually ends up being a good idea.
Especially if you park in the family garage and don't want them complaining about the gas smell.

So I need:
One line capped off and accessible for possible evap system later.

Yes, but if you use vacuum caps, check them regularly after about three months. Or make sure you use some old ones from the factory. Junkyard is a good place to grab a few. The ones you get from the auto parts stores are crap to the worst level you can imagine.
The only thing better than going to the junkyard is the old-school trick of using a short length of fuel hose (the good stuff though) and a screw or bolt siliconed into it.

What is the evap, large or small?

Good question. With the Can-P circuit and solenoid, usually a medium or small one from the canister. Old ones used the large port but attached before the throttle blades. So no full vacuum.
If you're out choosing your charcoal canister, I would opt for one with three sizes of ports. Usually two large ones (will have "mushroom" breather caps), one or two small ones (from the tank) and usually one medium size one. Approx. 5/16 or 3/8 inch fuel line size.
Member 904Bronco here just installed another one on the '67 he's building. Maybe he'll see this and chime in with what size he used.

And one last clarification. From the driver side valve cover hole (Bronco Script covers) gets the hollowed out PCV valve as a 90 and goes to the inlet tube fitting between the MAF and the throttle body. This is the PCV clean return. Think I got it?

Yep. Exactly.
Or close enough at least...;)
You can use a hollowed out valve to get the full 90 degrees, but the typical part is a 45 degree plastic elbow with a grommet. Depends on what size fitting you use I guess, as to which one is easier, but most of the time they're the larger hose size of the elbow, rather than the smaller 3/8" size hose of a hollowed out valve.
But either can work!

Just as long as it's behind the MAF sensor (so it's part of what has already been metered into the engine) and ahead of the throttle body (so it does not get full vacuum) you're good.

Paul
 

904Bronco

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San Martin, CA
Canister purge uses full vacuum. 1/4" > 5/16" port

The solenoid is active/open when you are at cruise 2000-2200 rpm or so.

You need to find a Mustang to steal parts from... There is an intermediate two wire harness that you need from the solenoid to the plug on EFI Guy's revised harness. And the 90* adapter off the CC has a connector on it that has a restriction in it.

I will post pictures of individual pieces later tonight.

Here it is on my 71...

So replacement CC from O'Reilly's, it does not come with mushroom caps. One of the Truck vendors sells them for like $1.60 a piece, or source from Wreaking yard.
Solenoid, you can buy new, but...
Intermediate harness, 90* elbow with connector. I opened the two I have and they have no restrictor in them?? Puzzling?? As my 71 has a restrictor.
CC has a small 1/4" port from the tank(s) and a larger port for the purge.
 

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904Bronco

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1/4 coolant hoses to upper manifold are de-icers.

Most people disable them, however you living in NJ you might want to keep them. I ordered 1/4" silicon heater hose from Summit with some EFI hose clamps on mine. I do tend to keep things the way they were from the Factory, just a personal preference...

You will get there Griz, and you will be an expect when you are done ;D
 
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John Griswold

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May 3, 2010
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Loc.
Medford, NJ
What is the charcoal canister from to get replacement from O'Reilly's?
What year or years mustang am I looking for to get intermediate harness for solenoid?
Only two lines to charcoal canister, 1/4" from tank and 1/4 of 5/16" to manifold vacuum with solenoid between canister and manifold?
What do you have at the tank? Is it a check valve to prevent gas from over filling going to the canister? I'm seeing it called a roll over check valve in places?
Thanks
 

Broncobowsher

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Jun 4, 2002
Messages
34,833
The PCV on the bottom is actually a neat piece of engineering. There are 2 fitting (front and rear) at the very bottom of the intake. The lines Tee together before going into the PCV. This was all done with a purpose. If you get any fluid into the intake (blowby, water splashed in) it can settle at the bottom of the plenum. When the engine is shut off gravity will drain it down and dump it into the crankcase via the PCV. Look at the lines as built by the factory and they have a downward slope to them.

This was done for a reason, and I have seen it happen on other engines. If the liquid accumulates enough it can start to pour into the rear most cylinder. Better to have the oil drain back into the crankcase. Even a little water is no big deal in the crankcase (heat will vaporize it). The one I know really killed an engine was a hard run and the second stage of the intake opened, running a slug of fluid into the cylinder at speed.
Ford engineered a drain for a reason, I made sure to keep it.
 

DirtDonk

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The roll-over check valve is usually either right at the tank, or near it. It's not really there to keep gas from going up the line if over-filled because you don't usually fill the tank that high (but it would help stop it if you did manage to get that far). But literally in a roll over your gas won't leak out all over the road.
At that point, the charcoal media in the canister getting hurt by liquid gas is the least of your worries.

You can see the two caps on the large ports of the canister. They're not really "caps" per sé, but allow the two ports to remain open without getting debris inside. Ambient air from outside is needed to allow free flowing of the vapors from inside to go up the small pipe to the engine.

At least that was my assumption. I don't think I've ever seen it written, but they've always used at least one of the large ports open to the outside atmosphere.

Paul
 

904Bronco

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What is the charcoal canister from to get replacement from O'Reilly's?
What year or years mustang am I looking for to get intermediate harness for solenoid?
Only two lines to charcoal canister, 1/4" from tank and 1/4 of 5/16" to manifold vacuum with solenoid between canister and manifold?
What do you have at the tank? Is it a check valve to prevent gas from over filling going to the canister? I'm seeing it called a roll over check valve in places?
Thanks

88-93 Ford mustang 5.0 A lot of the vehicles from that era used the same canister, just configured differently.
Harness same years, 4 cylinders are the same as the 5.0, solenoid too.
Yes 1/4 from tank, 5/16 to purge...
Areo tank with vent/rollover valve on top. Yes it has a check valve in it... Not for overfilling tank.
 
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John Griswold

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May 3, 2010
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Loc.
Medford, NJ
Thanks guys for all the help. As a whole project it is very overwhelming but as i ask questions about individual portions it becomes much easier to absord. We are very fortunate to have a resource like this with knowledgeable people willing to help out.
Thanks again, you will be hearing from me again soon i am sure.
 
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