Vacuum leaks

[James Morse]

So the shop looked at a/c which actually wasn't on the list but topped off freon 3/8 lb low that's always good to know it's full. And he said the valve for the heater core is not closing when Max AC is on so that says vacuum leak. He applied vacuum to it and valve itself is fine (it's actually new... yeah I know new doesn't necessarily mean good, but he says it's good).
Other symptom which I had noticed just last week, if you have Max AC on, somehow the air feed to the center dash vent, where it comes out really strong, gets shut off. If you change the selelctor you can open it again but after a while it will go shut again and I would guess that is also a vacuum problem and probably once I find where the problem is it will likely cure both these things. AC is working well other parts of system are fine he says and it's not like I have no ac it's just that I need to trace where is it leaking which I would rather do myself if I can he said it's just charge by the hour if he does it and I would think it's not that hard (although I have no vacuum testing tools). Help?

 

[ericbphoto]

The “valve” you are referring to is often called the “blend door”. It’s a vacuum operated damper in the ductwork that directs the air different ways for different functions. With no vacuum, the blend doors default to “defrost” operation which sends all the air up to the windshield. The vacuum line has a reservoir in it. On some trucks the reservoir is ball shaped about 3-4” diameter. On some newer trucks, like my 93, it is shaped like a medicine capsule or submarine. It is located on the passenger side in the engine compartment. There should be a sticker on your radiator core support (if it hasn’t been destroyed) with a complete vacuum drawing to help you trace out the lines and find the leak.

 

[franklin2]

Are you sure he is not talking about the water valve on some of these ranger trucks? We add this valve on the bigger trucks and hook the vacuum to the vacuum door at the pass side hood hinge so it turns the water off to the heater core in max position. We get it from one of the late 90's rangers, I forget which year.

 

[ericbphoto]

Are you sure he is not talking about the water valve on some of these ranger trucks? We add this valve on the bigger trucks and hook the vacuum to the vacuum door at the pass side hood hinge so it turns the water off to the heater core in max position. We get it from one of the late 90's rangers, I forget which year.

That’s possible. But he mentions air not coming out of the center vents. Either way, both functions are vacuum controlled.

 

[RonD]

Look under the Glove box you will see a white vacuum line, it looks like a wire
(May have to pull down the under dash cover, its usually just "wedged" in)
It will have a splitter(T) on it, it comes from the Climate control panel and splits to go to the Fresh Air Vent vacuum "motor", yes that is what they are called, lol, and it goes to/thru firewall and changes to a Grey vacuum line that runs to the Heater By-pass valve
These both get Vacuum when MAX AC is selected

Could be the Fresh Air vent line is unplugged

If you fold down the glove box all the way and look to the left you should see Multi-Colored vacuum hoses
That's the Vacuum Connector for the Climate Control Panels vacuum switch and the Trucks dash Vacuum Motors
It allows you to replace climate control panel without redoing all the vacuum lines

Anyway, you can unplug it and then test each line/hose going to the vacuum motors to make sure they "hold vacuum"
If so then Control panel may be the issue

If you notice changes in vents when accelerating then your Vacuum reservoir system is leaking


And the heater by-pass "leak" is not a Vacuum Leak like an engine vacuum leak, it is on a separate system that has a Vacuum reservoir so it will never effect engine operation

 

[ericbphoto]

James, This may be helpful. This doesn't show the heater coolant bypass valve. But the rest of it should be similar enough for your purposes.

 

[James Morse]

Yes franklin2 it's the water valve also the center vents (2 symptoms) in case you didn't gather that from the other posts.
I think actually it does happen on acceleration (revert to defrost) not sure but seems like it.
Side comment, interesting about the outside air door, lot of vehicles have separate switch for that.
So yeah I have the sticker on the truck, also found huge section in the shop manual about all of it.
Now my question is what tool do I want to test. Shop manual says Rotunda 014-R-1054, probably can't find that, there are other Rotunda but they are like $300+, that seems like overkill... what's a decent one? They have lot of tests, like, you can test the control unit too (doubt it's that) and they tell you it shouldn't lose more than so much per minute etc.
Manual has some good info also how to test your tester lol. Got a kick out of this one: symptom - "A/C working ok" - action to take "explain to customer how a/c works"
Anyway they have a ton of diag tests in there I think I'd start with their pinpoint tests to find where is leak. Shop manual nice to have they even tell you how to repair section of hose.

The slamming shut of the center vent door (so it all goes to defrost) I just discovered last week so I knew about that. Water valve and/or fresh air vent not closing I didn't know about - you wouldn't know because it still blows cold, just not as cold as it should I suppose. Weather just got brutal hot lately and I bought truck in fall so probably it was always like that and I just never ran into it yet. Here's the funny thing, I didn't even ask them to look at a/c, I was talking to them about Lexus a/c (it blows totally hot air) and they got the wires crossed, but turns out I guess the mistake was ok, I have no idea what 3/8 lb low means but I guess one would want to know it's charged ok with freon.

Anyway I think I need a tool, shop said they can fix it but it's costly time and I'd really rather do it, if I have to replace reservoir I'd do it... and/or old leaky or disconnected or plugged vacuum line somewhere and/or reservoir. Thanks for all the help.

 

[ericbphoto]

You can do a lot of inspection and checking without buying a special vacuum testing tool, unless you just feel like buying a specialty tool. Trace out the hoses and look at them. You’ll probably see a spot where a hose or elbow or tee fitting is cracked or worn through. Disconnect the reservoir and blow into it to see if it builds pressure and holds. Do the simple stuff first.

 

[RonD]

You need a length vacuum hose, actually get a few sizes, its sold by the foot in any auto parts store, and also some splices in sizes that match hoses

The hard plastic vacuum lines used in engine bay are just cheaper but can be replaced or repaired with rubber hoses

Vacuum reservoirs can crack but last thing to check, unless there has been front end damages on passenger side, that is where the reservoir is, in front of passenger side inner fender and bumper, so down low

But it has a black plastic vacuum line that runs along frame rail to the firewall and into the cab, this is the Vacuum source for the vent controller
This line can crack or melt(near exhaust pipe) but can be repair with correct size rubber hose, snug fit is all you need, no clamps as its Vacuum inside, so "pulls" connections together, unlike hoses with internal pressure that pushes connections apart and needs clamps

The Vacuum reservoir gets vacuum from the intake but thru an inline check valve, usually black and white plastic with a nipple for a hose on each side
Like the Check Valve on power brake booster


So back to how to test for vacuum leaks
Get a length of vacuum hose and splice it to the main vacuum line going to the cab from reservoir
The black line
Suck on the hose
If it holds vacuum, i.e. you don't have to keep sucking on it, then all is well
If it doesn't hold vacuum then there is a leak
Inspect the main line(on frame rail), that's usually where its leaking

A vacuum gauge on this system doesn't really help much, and a vacuum pump........well you have lungs that work just fine, suck on a line
Never BLOW hard into vacuum lines, as they have no clamps so you can blow an end off


This diagram may be hard to read but has the correct colors used by Ford inside the cab for the vacuum motors/solenoids

https://cimg1.ibsrv.net/gimg/www.ford-trucks.com-vbulletin/1472x976/untitled_2_3d05a093c007b1f4ebedddc14f3d819f9d7c719b.jpg

It doesn't show the "T" on the White line but its there, and the other white hose runs from the "T" to firewall at the same place the black line from the reservoir comes in

The Blend Door in 1995 and up Rangers is Electric, not vacuum operated

 

[James Morse]

Fantastic. Thanks.

 

[James Morse]

In pic at the bottom I see the black and the white lines. Black coming from the reservoir. White like you say T-s and goes to the recirculate door (can see it on the right) and to the heater valve.
So is the little black one where I should cut it and test and splice back together when done? To start anyway.

What's the 1/4" rubber line at the top of the pic? It runs up in there behind the dash.

 

[James Morse]

Where's the vacuum check valve? Not saying that's an issue, just, I don't see one. I mean, I see it on the picture, and the shop manual discusses it as possible source of lack of vacuum but I can't find it.
I'd think you have to have one. Maybe I'm just not seeing it yet.
Edit. I think the fat hose goes to the right dash vent... guessing.
As to the check valve if there isn't one wouldn't that make the reservoir basically useless? The book says there is the one side goes to the engine and the other side has two fittings I imagine one goes to the reservoir and one to the supply (through the firewall). Seems like that's the only way the reservoir could work.
This is the only connection between the reservoir and the manifold vacuum source, it doesn't look like a check valve at all. I didn't pull it apart to see, but it just looks like a regular connector.

 

[ericbphoto]

The check valve is probably in the engine compartment, between the vacuum source and the reservoir. It’s purpose is to hold vacuum inn the reservoir and the rest of the circuit when there is little or no vacuum being generated in the intake manifold.

 

[James Morse]

Eric see pic I'm not finding it.
I don't get why there's be 3 connections on it. one I get, for engine vacuum, another I get, goes to reservoir. where's the other connection go?

 

[ericbphoto]

Eric see pic I'm not finding it.
I don't get why there's be 3 connections on it. one I get, for engine vacuum, another I get, goes to reservoir. where's the other connection go?

The one in the diagram I posted has 2 outlets. But they go to a common cavity inside. Yours may only have one inlet and one outlet. It could be the part you show in your picture. If so, then there is probably a tee in the line so it can supply vacuum to the reservoir and through the wall to the controls.