97 Aero. Just recently experienced this weird issue. Had the AC on for a warm day and heading down the freeway at 70mph. The AC is kicking out some nice cool air. Noticed that when the van was heading up a slight grade, the air speed comming out of the vent would slowly diminish until no air came through the vents at all. As soon as the van leveled out or started heading downhill, the vent air speed would pick back up and blow normally. This happened repeatedly. Is this a blower issue? Vent door issue? Something else????? Since the van was traveling at speed, I could not tell is the blower was still blowing when I was experiencing no air out of the vents.

 

you have a vacuum leak in the small vacuum lines running into the firewal heater box from the engine compartment or in the vacuum reservoir tank mounted on the firewall at center or in the vacuum line that feeds the tank from the engine manifold

the heater/ a/c control doors for air flow are all controlled by vacuum, no electrical. the heater a/c selector is a vacuum selector valve.

 

Is there a good way to tech this out?

 

Don't overlook the check valve in the vacuum line to the climate control system. There's a check valve that will trap pressure in the system when the manifold vacuum drops. If it's not working, the damper doors move when you climb a hill. You can check the check valve by removing it and blowing through it from both ends (separately, of course). It should only allow flow in one direction.

It looks something like the one shown here, but it's black and white.

McMaster-Carr

 

where is this check valve located on the aero?

 

It's hard to describe where, but I can tell you how to find it. It's located under the hood in the vacuum line to the climate control system. If you find the octopus on the intake manifold, look for the small diameter (about 1/8") nylon tubing. The tubing has a black rubber fitting on it that adapts from the nylon to the port on the octopus fitting. Anyway, trace the tubing from the manifold towards the climate control system under the hood and you'll see it. If I remember correctly, it's about the same diameter as a nickel - maybe a little bigger or a little smaller. The nylon tubing on either side of the check valve has a rubber fitting on it to step up from the small diameter nylon to the large diameter inlet/outlet of the check valve. The check valve can be somewhat of a pain to remove as those barbs seem to dig into the rubber pretty well.

 

I found this and did check it for function. It would flow freely in one direction and took quite a while to close on low vaccuum. I'm presuming this is the culprit. Now where can I purchase it. Looks pretty simple and generic. Tried over at O'Reilys and Advance auto and both had nothing specific or generic. Any idea's?

 

I'm gonna have to disagree in part. The leak does NOT have to be in the hoses that are part of the vent and blend controls, any severe vacuum leak in any other system can cause the exact same problem. On my van, a faulty EGR tube seal was the culprit, definitely not part of the climate controls.

So sorry if that doesn't help, the leak could be anywhere. You can inspect all the lines carefully for breaks, replace any hoses that are cracked or split.

Once again, for those that recommend spraying flammable liquids to locate the leak, on my van, we knew where the leak was, it was a massive leak. We sprayed all around it, and guess what, the idle did not change at all. Not really surprised, as I have never seen that technique every actually work myself. I had another vacuum leak in one of the hoses too, it didn't respond to being sprayed directly either. This technique I could only see working on a vehicle that has no idle controller, or the idle controller is sluggish, otherwise the computer will probably adjust the idle faster than you can detect the change. This technique does however work if you watch the fuel trims while you spray the leak, the STFT% will drop as a strong negative value while you spray the leak. However that requires that you have a scan tool that can read live PIDs.

We found my leaks with a smoke machine. They hooked up the machine, had the first leak located in minutes. The leak I had later took longer to find, had to pull the doghouse first. I have yet another leak currently, I'm just gonna replace all the lines that haven't already been changed just to make sure I get it this time. My intake gaskets have already been replaced with the updated Motorcraft ones. For the record, on the '97 at least, don't waste your time and money with the FEL-PRO gaskets, they will leak almost every time. Ford came up with an updated design that is much better. The Fel-Pros are great on the models with the metal upper intake, but the plastic ones need the updated Motorcraft gaskets to seal properly.

 

You can disable the IAC to do the spray test. Just turn up idle plate stop screw so the engine doesn't stall. Then the EEC can't adjust the idle, only the mixture from reading the EGO, which does not respond that fast.

 

check valve
call around to the auto parts stores for one that will order Dorman for you.
Dorman Vacuum Check Valve
PART#:
RB47149
MFR#:
47149


DORMAN VACUUM CHECK VALVE -- One-way check valve; Maintains and used in vacuum systems with any vacuum operated accessory.

Rockauto carries them
DORMAN Part # 47149 More Information About this Part Vacuum Check Valve Application Universal
Category: Vacuum Valve

Part Image
$3.24

 

Went to Ford dealer to get the exact replacement part. Even though it is a $1.00 part, I was willing to pay $10 for it. The guy at the counter got pretty quiet and finally printed off a diagram. Is this what you are looking for, yup, there it was. His response, discontinued. Ok, what replaces it, Nothing! He did a lookup to find out if another dealer had it and a few popped up. He said here is the real bad news, since its obsolete, the price is $126.00 dollars. Give me a break!!!!!

 

I guess that's because they added shipping.

 

I got quoted a ridiculous price when it wasn't obsolete about 10 years ago. It turns out that what you are getting is an "assembly" which includes the nylon tubing and the various endfittings. Still a ripoff. That's why I got mine from McMaster Carr with some adapters to step up to the rubber fitting. Since then, I've seen the part at a local Napa and I think Pep Boys in one of those blister packs that says Help! on it or something like that. They usually have oddball parts like that. You might not find your exact part, but you should be able to find something you can adapt. Power brake systems use them in the vacuum booster line, but the size may be too big.

 

BillyBob Ford's corporate jet must have needed to be refueled this month. Price of Jet A is up.

Last time in to Ford parts counter for valve stem seals for a 4.0L. $4 a seal ring. Jesus H. Christ. package said made in China

 

Many years ago, I went to my local dealer (no longer there) to buy these little rubbing pads that went between the frame that held the side glass and the rails that they slid up and down on. It's a little piece of plastic about 3/4" long, 1/2" wide, maybe 1/4" thick, and had a nub on it that inserted into a slot on the frame. I think it was $4 each. The funny thing is, a day after I purchased a couple, I found some pieces of plastic that looked EXACTLY like those things from some place else, but came 10 to a package for about $2.

I think the bulk of the costs of parts at your dealership is in the packaging, stocking, and handling. Most little parts like that come off of the machines that make them for pennies each. They get packed in boxes of 1000 or so when they're sent off to the assembly plants, and they're still cheap. But if they're packed 1 or 2 to a box intended to be sent to a retail store, their MSRP end up being 100 times more. But criminy, $126 for a one-way vacuum valve seems beyond ludicrous. Time to look for them in a salvage yard.