97 2.3 air vent issues

[3ncrypt3d]

Hey! Lately, my ranger has been having issues directing airflow. Today, no matter what setting I have it at, it just seems that air is coming out of the defrost area. I checked the actual switch itself, and it’s vacuum operated so I would assume I’m having vacuum issues. If anyone could help point me in the right direction, it would be much appreciated!

 

[Mark_88]

There should be a check valve under the hood on the passenger side. Mine was round about the size of a softball but yours might be different.

That controls the vacuum to the heater controls and may have became disconnected if you were in there changing plugs or the air filter...or just through decaying parts. Check that and then follow the line back to the source on the intake.

If the engine is running or idling rough there may be a vacuum leak somewhere but if not it's probably the check valve.

These are not complicated systems but they do require a bit of time to trace everything. The vacuum connector in the dash has four of five postes and the rubber boot just slips over them. They can become dislodged also if you were recently working on your radio or something else like the GEM module that is also located in that area (or was on my 96).

Usually a rough idle if any vacuum lines are disconnected as mentioned before.

 

[3ncrypt3d]

There should be a check valve under the hood on the passenger side. Mine was round about the size of a softball but yours might be different.

That controls the vacuum to the heater controls and may have became disconnected if you were in there changing plugs or the air filter...or just through decaying parts. Check that and then follow the line back to the source on the intake.

If the engine is running or idling rough there may be a vacuum leak somewhere but if not it's probably the check valve.

These are not complicated systems but they do require a bit of time to trace everything. The vacuum connector in the dash has four of five postes and the rubber boot just slips over them. They can become dislodged also if you were recently working on your radio or something else like the GEM module that is also located in that area (or was on my 96).

Usually a rough idle if any vacuum lines are disconnected as mentioned before.

I found 2 softball size balls there, both of them look to be in good condition. I did check the in dash connector, and that was fine. I’m assuming it should have vacuum when the engine is running? If so, mine didn’t. My engine is running fine, no rough idle or anything. Just my air vents are messed up.

Edit: Would the vacuum for cruise control and the air vents be one whole system? Or separate ones. My cruise control works fine. It does look like those two balls are connected via various hoses, but I don’t want to assume anything.

 

[RonD]

The dash air vents are run by Vacuum, it does come from intake manifold but it needs constant and stable vacuum all the time, so it gets its vacuum from a Vacuum Reservoir.

Black Plastic ball, looks like this: https://images-na.ssl-images-amazon.com/images/I/71PQeoayANL._AC_UL320_SR288,320_.jpg

It is usually located on passenger side at the front of engine bay way down low, often hard to see.

If you look at passenger side Firewall you should see two plastic vacuum lines coming out, a Grey one and a Black one
Grey one goes to Heater Hose valve
Black one is the one you want to follow to the Vacuum reservoir ball
And you will most likely find the BREAK in this hard plastic line while following it, they do get brittle and the exhaust is right there so............
It can be repaired using regular rubber vacuum line slid over the hard line

95% of the time the black plastic vacuum line from firewall to reservoir is leaking
Other 5% of the time the Reservoir ball has cracked

The reservoir has two black lines connected, the "other line" goes to the intake manifold, it will have a Check Valve inline and then connect to intakes vacuum manifold

Intake manifold-----------check valve---Reservoir------------------(firewall)------Vent Control


Defrost air flow is the Default vent setting, when other vents are closed, or there is no vacuum.
If you have a small leak in the system you might notice Dash vent air flow dropping off or going off completely when you accelerate, that's because intake vacuum drops close to 0 at that time, if Reservoir isn't holding a vacuum reserve then Vents close and Defrost gets all the air

 

[3ncrypt3d]

The dash air vents are run by Vacuum, it does come from intake manifold but it needs constant and stable vacuum all the time, so it gets its vacuum from a Vacuum Reservoir.

Black Plastic ball, looks like this: https://images-na.ssl-images-amazon.com/images/I/71PQeoayANL._AC_UL320_SR288,320_.jpg

It is usually located on passenger side at the front of engine bay way down low, often hard to see.

If you look at passenger side Firewall you should see two plastic vacuum lines coming out, a Grey one and a Black one
Grey one goes to Heater Hose valve
Black one is the one you want to follow to the Vacuum reservoir ball
And you will most likely find the BREAK in this hard plastic line while following it, they do get brittle and the exhaust is right there so............
It can be repaired using regular rubber vacuum line slid over the hard line

95% of the time the black plastic vacuum line from firewall to reservoir is leaking
Other 5% of the time the Reservoir ball has cracked

The reservoir has two black lines connected, the "other line" goes to the intake manifold, it will have a Check Valve inline and then connect to intakes vacuum manifold

Intake manifold-----------check valve---Reservoir------------------(firewall)------Vent Control


Defrost air flow is the Default vent setting, when other vents are closed, no vacuum.
If you have a small leak in the system you might notice Dash vent air flow dropping off or going off completely when you accelerate, that's because intake vacuum drops close to 0 at that time, if Reservoir isn't holding a vacuum reserve then Vents close and Defrost gets all the air

I checked the vacuum hose as far back as I could, but I can’t trace it once it goes under the blower motor, and air conditioning stuff. From the hose that I can see, it looks fine. I also took the reservoir out, plugged the holes, and put it water to see if it was leaking. It’s not. So I have no clue what’s wrong.

 

[RonD]

If possible suck on the black line going into the cab, it should hold vacuum, if it doesn't then have someone inside to see if they can hear where it is leaking.
Do NOT use an air compressor to test vacuum hoses for leaks, you WILL blow off connections and end up with lots of leaks

Disconnect and then follow the "other" line from reservoir to upper intakes vacuum manifold.

Remove that hose from intake and BLOW into it, the in line Check Valve should NOT allow you to blow in pressure, it should only allow suction/vacuum pressure
BUT...........with engine idling, high vacuum, the vents should still work even if check valve is bad, so long shot on that.
But you still need to make sure the Vacuum Source for the reservoir is hooked up so it has vacuum stored

 

[3ncrypt3d]

If possible suck on the black line going into the cab, it should hold vacuum, if it doesn't then have someone inside to see if they can hear where it is leaking.
Do NOT use an air compressor to test vacuum hoses for leaks, you WILL blow off connections and end up with lots of leaks

Disconnect and then follow the "other" line from reservoir to upper intakes vacuum manifold.

Remove that hose from intake and BLOW into it, the in line Check Valve should NOT allow you to blow in pressure, it should only allow suction/vacuum pressure
BUT...........with engine idling, high vacuum, the vents should still work even if check valve is bad, so long shot on that.
But you still need to make sure the Vacuum Source for the reservoir is hooked up so it has vacuum stored

The hose going into the cab holds vacuum, so that’s not it. The other hose that comes from the air intake, doesn’t allow pressure in, so that’s not it. But, after plugging all those hoses back in, it works again. I have no idea how or why. All the hoses are in surprisingly good condition, for a 20 year old truck so I don’t thing there’s any leaks there... But at least it’s working again.

 

[Mark_88]

Did you check the connections and maybe reverse them? If they were on backwards it might explain why it started working or if the connections were loose. Those rubber connectors can get sloppy and allow air in/out. A bit of moisture helps seal them for a while.

I used to clip the ends of the hoses when connections got sloppy and I also collected spares every time I went to the yard if possible. Had one of those compartment containers with all kinds of replacement parts...still have some...

 

[RonD]

Good work

Yes, as Mark_88 said, some vacuum reservoirs have built in check valve on one port so only work in one direction

 

[tomw]

The action of blowing into the check valve may have dislodged a piece of 'stuff' that was sitting on the valve seat, allowing it to function once again. As in the above 'word chain', the check valve would be 'before' the reservoir and 'before' the line going into the cab.

This:
Intake manifold--check valve--Reservoir----(firewall)------Vent Control

There can also be vacuum 'taps' to things such as the power brake booster which would 'tee' into the line coming from the reservoir.
If it was built into the reservoir, just poking around could 'fix' it.
FWIW, you can get a check valve at the HELP section, and splice it into the line from the intake leading to the reservoir, and it will make the reservoir work again without messing under the dash or removing the reservoir.
tom

 

[3ncrypt3d]

Well, no avail. Today turned it on, and it has the same issue. Would it be a good idea to replace all the vacuum hoses that I can? Some of the ends did seem a little loose, but they’re still holding on. I’m going to a local yard tomorrow, so I can see if I can get some ends, as Mark_88 suggested.

 

[RonD]

I would first see if the cab system holds a vacuum, use Black hose from firewall to Reservoir to test this
Put Cab vent selector in each position and then suck on that hose to see if any of the vacuum motors or hoses are leaking
Fresh and Recirculated air vent also uses vacuum motor so test it in both positions

If it holds vacuum in all positions then problem will be in engine bay

The reason vacuum hose fittings don't use clamps is because they tend tighten when vacuum is applied so really don't need clamps.
But that also means if you are reaching around in engine bay or under the dash with engine off, no vacuum, these hoses can be disconnected without you being aware of it.

The grey line that goes to heater hose valve gets its vacuum from the black line/reservoir but from inside the cab, so make sure it is in good condition

You can also by pass the reservoir and use a "jumper" vacuum hose directly to the intake manifold, with engine idling, high vacuum, the vents should all work if the hoses and vacuum motors in the cab are OK

 

[3ncrypt3d]

I would first see if the cab system holds a vacuum, use Black hose from firewall to Reservoir to test this
Put Cab vent selector in each position and then suck on that hose to see if any of the vacuum motors or hoses are leaking
Fresh and Recirculated air vent also uses vacuum motor so test it in both positions

If it holds vacuum in all positions then problem will be in engine bay

The reason vacuum hose fittings don't use clamps is because they tend tighten when vacuum is applied so really don't need clamps.
But that also means if you are reaching around in engine bay or under the dash with engine off, no vacuum, these hoses can be disconnected without you being aware of it.

The grey line that goes to heater hose valve gets its vacuum from the black line/reservoir but from inside the cab, so make sure it is in good condition

You can also by pass the reservoir and use a "jumper" vacuum hose directly to the intake manifold, with engine idling, high vacuum, the vents should all work if the hoses and vacuum motors in the cab are OK

So, I tested the line going into the cab, and that holds vacuum. I unplugged each vacuum hose and tested each one individually, and they’re good too. After plugging them all back in, it’s working again. My working theory is that some of the rubber ends are just old and worn, so I’m gonna try and replace those.

 

[3ncrypt3d]

Well bad news. I’m pretty sure it’s leaking air from the cruise control, because the main vacuum line goes to both. If I plug off the cruise control, it works flawlessly. So that’s my current predicament

 

[Mark_88]

At least you figured out why the vents are not working and you got some good experience with the troubleshooting.

I've never had cruise on a Ranger so no idea what module to replace or how they work. There should be some information on it in the on-line manual but I've never bothered to look for obvious reasons.

If you want to have a look there you can through the link below...

http://www.therangerstation.com/forums/showthread.php?t=170166

I was on there a few days ago and it worked so we are not blocked on that yet...