Just looking for confirmation before I start cutting vacuum lines & buying a new vacuum reservoir box.
I have the 2003 model year E-350 with 7.3 Diesel. Getting the ol' default blowing to the defroster because I lost vacuum.
Pulled line off coupling on passenger side under hood. (Sucks there). But then the line disappeared down the side into what I have been reading is a non accessible area (wheel well), where there is some reservoir box with a check valve? (Known problem area when you have suction loss on through the firewall & up to the selector switch?). When I jiggle that line it does sound like it could be floating free in that area BUT does not pull out.
So I just am asking if I DO INDEED also have this reservoir box in there & that I should go with the plan of just buying a new box (with check valve integral) & relocating it somewhere in the cab (accessible)???? And on to the selector switch?????
Looks to me that it would be easier to send a new line through on the drivers side firewall & feed it up in driver side foot area, & mount the new box there vs. that crowded passenger side area the OEM sent the line & presumably buried the reservoir somewhere in between the sheet metal of the wheel well. Any of this sound right????????????????????????

 

I recall an option is to run a fresh line from the engine through somewhere by the doghouse into the passenger footwell area where many hang a replacement reservoir.

If that isn’t in JWA’s excellent and comprehensive AC system thread, check YouTube. Here’s one with spooky music - https://www.youtube.com/watch?v=Tb661UrsYX0

Sixto
07 E350 5.4 178K miles

 

@tabijan
Let me ask again.... It seems all the write-ups/posts on this talk about the need for this check valve & reservoir. Talk about how when they accelerate they lose engine vacuum and thus vacuum needed to hold cans in position they are set for. BUT I have a diesel engine & it has an independent, belt driven vacuum pump that creates the vacuum necessary for all vacuum assisted or operated stuff. So I am wondering if I even have a vacuum reservoir or a check valve as those items seem to be necessary for vehicles that would suffer a loss of supply vacuum when you open up the intake manifold by heavy acceleration (IE: Gas engines). In my case I think I would get even more vacuum when I accelerate because it causes the drive belt that spins the vacuum pump to spin faster!
So I am trying to figure if I can just replace the line right off the main vacuum supply block & send it right through to the selector switch? No need for reservoirs or check valves? And wondering if that OEM line that currently disappears down into the passenger side area even actually goes to a hidden reservoir in the wheel well area or if that's just where they route it on all vehicles but because it's a diesel with a separate continuous duty vacuum pump they don't install any reservoir (or check valve)????
Just can't see why any of that is needed. As soon as the engine is running there is a constant vacuum supply. Maybe a reservoir & check valve smooths out any possible pressure fluctuations but I really can't grasp a reason it/they would be necessary????????
I have read a lot of JWA's post (and others) on this subject but have as yet to determine if they are talking strictly about gas engines?
Can anyone set me straight on if there is a difference between gas & diesel as far as the way vacuum is produced & how/why the systems are different?????? I'm looking/shopping for all these supplied part numbers for the box & valve but am wondering if I really need them????????

 

Once any steady vacuum signal reaches the check valve/reservoir the HVAC systems are the same. Regardless where the check valve/reservoir is located assuming it feeds the air flow duct soleniods its still the same system.

I guess you don't really need anything other than rock steady vacuum signal as in it never fluctuates do as you please with your own system. Ford installed the check valve/reservoir to avoid the uncommanded switch to defrost under loss of sufficient vacuum to maintain the floor or vent setting.

If your forego some parts you could always add them later.

 

Both of my 7.3 vans have a new line installed and the reservoir is omitted. Both work fine. I bought my 01 sight unseen. I had to ziptie the solenoid in the dash to get ac blowing on a hot June day in Sacramento for my trip to Kc. And completed the new line when i got it home.

 

Thanks JWA & T-wood
I almost forgot to check back to this post.
I went ahead & ordered the reservoir & check valve before I read your responses. Hate to spend money when it's not really called for but I guess it's to late now. Knowing myself I will probably run a line without the reservoir & valve temporarily just to see how it works out. If all seems well, Maybe I will put the items up for sale on eBay or on this site for a discount if I really don't need them.
It just seems that with the dedicated vacuum pump creating a pretty good suction as long as the drive belt is turning, there would not be any reason for a loss of Vacuum that would cause the any of the control cans to give up their positions while driving. Can't see any other reason to hold the vacuum when I shut her down. Anyway, I hope I remember to get back here to post results. Thanks guys

 

You guys better not be pulling my leg!! I just managed to cancel the order for the Reservoir Tank!!!!
Still going to use the check valve. Maybe i will just leave the long length of vacuum hose coiled up to serve as a mini tank.
I'm looking at saving about $23 bucks total for the tank,shipping & tax. Not a bank buster but if I don't really need it no sense in the extra connections or room it takes up.
I got your names so I know who to be mad at if it don't work!!! LOL

 

For myself I've offered advice to simply restore the use of factory parts in a somewhat original configuration even if their physical location is not consistent with a brand new E-Series build. Not being too snarky but if $23 makes that big a deal you'll have to deal with how the HVAC system does or does not function.

It's too easy criticizing the factory's designs 19 years after being built and yet when properly maintained most E- and F-Series trucks seem to work for a long time. I'm driving a 2000 E-250 and a 2003 E-350 (both with 5.4 gas engines, same HVAC) quite comfortably. When I've had to service my vacuum controls replacing parts was the order of the day using Ford branded parts. it was a one time thing and should last another 20+ years I'm sure.

 

Just to press JWA’s buttons, if a vacuum reservoir for consistent AC function was good idea, a plastic box beside the exhaust manifold was a bad idea

I followed JWA’s vacuum box in the passenger footwell advice on our 5.4 gasser and the AC’s been great since. Oddly, the electronic cruise control seems to work better too. No more dropping off on steep climbs.

Sixto
07 E350 5.4 178K miles

 

The factory-installed reservoir is a good 6 inches or more from the Bank 1 exhaust manifold. When it develops a leak it has more to do with age rather than close proximity. Keep in mind the evaporator and heater core case is closer and yet I've never heard of issues with cracks etc.

There's no IF whether the vacuum reservoir is a good idea----when the temporary loss of vacuum causes an annoying change of air flow its inclusion as a comfort feature has proven to be a good function since its introduction into most American-made vehicles.

Not sure why or how those two sub-systems affect one another---that's certainly an odd observation.

 

Ive never had a temporary loss of airflow in my vans. Both of my diesel vans were stuck on defrost when i got them. So i eliminated the leak. Now ive never eliminated the vaccum canister in a gas vehicle. A diesel motor doesnt create a vaccum on its own, so it has a vaccum pump. Idk if this makes the vaccum more reliable or more consistent. It could be the vac canister in a diesel is much like an appendix in a human.

 

My '78 Ford E250 van has vacuum canistors to help assist heater / ac door function.
Honestly, since 1993, I've never pulled the heater / ac control panel, and doors are still functioning.
There will come a day when I Will Have to Deal with getting an education once a hose splits, and repair begins.

I began a "Do-Over" of my van beginning August 2020, and have discovered I am dealing with Obsolete Parts sourcing issues.
Obsolete parts sourcing is the curse of driving one-off vehicles.
Another issue is that I am more Obsolete than my E250 by 27yrs.

Because of fuel mileage, my daily driver is a 2009 Honda CR-V running at 25mpg.
My '77 F-350 4x4 longbed crew cab pickup w/ 300 six and holley 4bbl gets 13mpg.
My '78 E-250 4x4 Chateau wagon w/ 429 and holley 4bbl gets probably 10mpg. (same as my son's 2007 Tundra w/ 35's).

 

Lots of talk here about vacuum reservoir (not cans), being a Good idea, Bad idea, Location...
The point I had been trying to address and now understand is related to
the fact that there is a difference between Gas & diesel motors & therefor
the need, (or not) for a vacuum reservoir in a diesel. As has been pointed out...With the diesel's,
there is really NO NEED for the reservoir because a diesel has a dedicated vacuum pump that runs
as long as the engine is running. Not like a gasser that uses engines intake manifold to draw it's
vacuum from.In which case there can be a LOSS of necessary vacuum to hold your HVAC system
flapper controlling cans in some set position under certain engine loading conditions. The diesel does
not face this issue SO.....There is really no need for the reservoir tank in the diesel engines vacuum lines/system.
As I may (or may not) have written earlier, I think ALL the vehicles just come down the production line with
the reservoir tanks & connected vacuum lines installed in that wheel well position with no concern as to
if the vehicle in question will be equipped with a gas or diesel engine. Having said that,
Knowing the way these auto company's employ (Bean Counters), I'm surprised this unnecessary part
for a diesel application has not been discovered & pulled out as the vehicle processes down the line.
Having said THAT. Maybe (they) do know & have already figured it would cost MORE in labor hours
for a man to remove it than it saves in cost of wasted part!
FINAL ANSWER for anyone that may come across this thread in the future. There is NO QUESTION
that the reservoir tank is ABSOLUTELY NOT NEEDED (or required) for your system to work properly
if you have a diesel.
The dedicated vacuum pump supplies all the vacuum you need during all phases of driving to
hold your vent/flapper control cans in whatever position you have set them in.
As to if a one way check valve is (required) could be debated. My opinion is it's good to have it.
It will hold the (flappers) in position for some time after engine shut down. Why this might be important
is again debatable.(I'm not really thinking it's of any real necessity). I choose to install it for nothing more than
the fact that I can manually suck a vacuum and hold my cans/flappers to blow the warm air out the dash vents
for these few winter months until I get around to drilling the new hole for the new vacuum line (WITHOUT RESERVOIR)
through the firewall directly off the vacuum pump port manifold (not engine manifold).
Basically, this means I got to suck off my van every day before it will blow me back some warm air! LOL
Make of that last statement what you will.
I'm not arguing here about Ford's decision to use or where they choose to locate the thing. Though locked inside the wheel well
seemed not very user/service friendly, I can understand that if built/installed correctly it could be expected to likely last
what (most) consider the life of a vehicle. And if you want to keep it longer just redesign it or deal with it however
you must. Obviously, Many here have choose to relocate a new reservoir tank (and lines) outside the wheel well area.
Others went ahead & cut into it to fix it in OEM fashion. (I think they really just wanted to see where it cracked & if
it was REALLY hidden in there!! LOL).
Anyway, EVen though I have not as yet hooked mine up to the pump. I am 100% confident all will function
correctly when I do
Thanks everyone on FTE for your input & the VAST knowledge base that is being provided by this site & members!!!!!!!!!!!

 

Dieseldogtom
Gas vs diesel means little for your problem
Your diesel simply has a vacuum pump to supply vacuum instead of the engine providing it
Other than that the vacuum systems are roughly the same
You will not see a pro bypassing the tank or can (reservoir)
The one way valve (check valves) fail regularly and yes the plastic tanks crack once in a while
Good luck real common problem. Not too tough to remove the inner fender panel for access

 

There are already quite a few work arounds or easy fixes for the HVAC system when its operation involves engine (or whatever) vacuum. From '92 forward the well-hidden plastic reservoir and check valve are easily and inexpensively bypassed or relocated from its original location. This is desirable due the factory-installed reservoir is nearly impossible to replace when the engine is in place.

Almost regardless the model year relocating the plastic reservoir without removing or cutting any body panels can be accomplished.

I've devised and used a process on 4 different E-Series to great success. Using new OEM parts it costs less than $40, can be easily accomplished by even an entry-level DIY'er with minimum tools. I've documented this here on FTE, can be easily found in the tech folder for E-Series vehicles.

Do it or not depending whether you want or need the air flow direction to function as it did when new.