Soooooooo most anyone with an E-Series where the heater air flow has needed repair too often it comes down to dealing with the vacuum reservoir and check valve so important to proper operation. The problem has always been WTF is it exactly? You can look nearly everywhere, you know its somewhere but yet its never found---until now.

My van is undergoing an engine swap so there's no better time looking for that elusive POS---sadly this is just about the only way to find and partially see this part. Even more sad is in order to R&R the existing part would require disassembling nearly the entire A/C Heating system including properly recovering the refrigerant. So without further adieu here's that F'n thing caught in its natural habitat, naked and exposed:

Inside the yellow box:




Zoomed in towards the back of the evaporator box near the metal firewall; pay attention to the yellow and red arrows:



Another same view, additional info:



The greenish lines show two gussets formed into the evaporator case---the reservoir is partially obscured by these which just adds to it being so difficult to see or find.


This is what we've been searching for, uninstalled of course:



The yellow arrow above relates to the yellow arrow in the second photo---they're pointing to the same portion of the vacuum reservoir. Note: The blue-green arrow points to what appears to be a bolt hole but its not---seems to be a flange that snaps into mating prongs on the evaporator case instead of using a threaded fastener.

The red arrow in photo #2 relates to this part, inner evaporator case:


That projection fits into the interior side of the evaporator case exiting outside the firewall--its the A/C condensate drain, this view:





Another view of the uninstalled reservoir:



The upturned flange on the opposite side ^^^ cannot be seen or felt by hand how its attached--guessing the same sort of snap-in-place fastener.


This one shows simulated vacuum tubing installed, the Ford check valve installed in what I believe would be similar to the factory installation:


Black to intake manifold, purple to dash mounted A/C system controller aka Function Control (Heat, Vent, Defrost etc)

Hopefully this shows how nearly impossible it is to access this part---it would require a complete disassembly of the A/C-Heater system inside the engine bay. I hate bashing Ford but WTF where they thinking with this idea? Did GM or Chrysler trick them into this design? I simply do not see any way possible to R&R this part any other way.

There have been a few great threads of improvised and self-fabricated vacuum reservoirs. For me its far easier buying the Ford parts and install them inside the cabin tucked up under the dashboard. Removing a few lower dashboard trim parts there's plenty of room for all this to fit neatly, cable ties holding it in place. I'll be doing that on the van shown and will probably post a different thread how that'll be done and the finished results.

I hope this is informative---I've been searching for this damn thing nigh on 10 years or so.

 

I just found mine due to no air flow from in your face vents on llloonnngg uphill pulls. 1994 E150 cargo, 5.8L. It is located behind the passenger headlamp and has two ports. The port with the red vacuum line from the intake has a check valve contained inside the tank. The sleeved two fuel line pieces replaced the slightly leaking two port rubber connector.

I learned the hard way that reversing those lines at the vacuum tank caused a Check Engine Light and codes related to Insufficient EGR flow and Thermactor operation.


Routing diagram on my van shown.

 

I've got that part just laying loose in the engine compartment. I've wondered what the heck it is.

 

We have a fleet of vans and they all have this vac reservoir. They last about 5 years. I've replaced them but it involves pulling the evaporator case which is a big job. It's much easier to do while I have the engine out. Rather than pull all of this apart I just relocate the reservoir inside the van on the right inner trim panel and run the vacuum line inside from the inner fenderwell area. You have to drill an access hole in the inner fender structure under the evaporator case which isn't a big deal.

 

I'll indeed do the relocation thing----in fact the van shown has already had a half-assed attempt at that now. I'm not sure why it doesn't do the job but once this is back to me I'll be re-routing the vacuum signal, install the new reservoir and check valve. Using silicone vacuum tubing should assure it won't degrade over time and will hold its connection to the various fittings.

I really can't think of any scenario where trying to replace this thing would be a good idea. There are a ton of great alternative spots even inside the engine bay so why it ends up where you see it baffles me. When the weather is better I might cruise the scrap yards for an E-Series where most of the engine, evaporator case and most other components on the right side have already been taken, see what's to see just to better understand all this.

Thanks for the reply MPH---appreciate it.

 

JWA, this is a great find! Does one have to do a complete engine removal to find that part!???

Engine swap? I had no idea. Did you find a new used engine? Are you doing this yourself?

 

Hey CoolFeet! The entire outer evaporator case would have to come out I'm guessing. At minimum the battery, battery tray and whatever else is directly in front of the evap case is in the way. Having had the battery tray out that's somewhat easy, all things considered.

Here's two links about my motor ordeal---they're lengthy so be prepared to invest a bit of time or ignore them---they're just for information more than any sort of how-to etc.

Reman'd Engine Fresh Install & Break In

Warranty Repair Issues

This engine is directly from Ford, bought through the local dealership's parts counter. As I don't have a place or the heavier tools swapping the engine requires this was hired out to a trusted shop. That shop is also now doing the warranty repair work which involves an inspection to justify to Ford Powertrain Warranty Center another complete engine is necessary.

 

Good Grief! I'm appreciating the reservoir placement in my '82 E350, despite blood loss during replacement!

 

It seems no matter what year E-Series we have these vacuum reservoirs are a huge PITA, some more so than others.

 

I moved mine inside, under the dash and my AC is still going to the defrost, I'm gonna pull the doghouse one last time, change out my hose, and a new check valve.

 

I found an OEM reservoir on FleaBay or Amazon---shipped and delivered for less than $20, the OEM check valve was about $10 and as you say Maples01 moving it inside is easy and the better place I think. If further repairs are needed we know right where the components are.

The OEM check valve is nice and has three connections, one for the vacuum source (intake) and two on the other side where one leads to the air distribution system, the other to the vacuum reservoir itself. Even if the source side is disconnected the check valve maintains the vacuum in the reservoir as it should----this is how the selected vent positions are maintained under harder acceleration---the leaking systems will temporarily default to defrost and return when vacuum has been stabilized.

 

I wanted to pull the red line from the front and run it inside but no help was available, so I cut it, hooked up my check valve to the rubber line I connected to the intake, pulling my plastic line that is on my canister through the bolt hole to the other side of the check valve, my canister has 2 hoses on it, I think it came from an old Mustang. I bought a small check valve, it's not the large one with 3 connections, it may not be working properly, allowing bleed off, guess I need to redo it, really tired of it cutting to defrost because when it does, the rear goes to heat.

 

I made the reservoir from a piece of 2 in pvc and completely bypassed the factory system. No more problems.