Air Box Vaccum Line Topic is solved

[abscate]

You can’t assume the thermostat operates the same on a pressure differential as opposed To designed working pressures without knowing more about the inside. Those don’t fail in our experience , it’s vacuum hoses and fitting ends that fail on this system, or snapping off the nipples with gorilla techniques

[MrAl]

Hello again,

I am only assuming it works that way pending an actual test. All of the thermostats i have seen that control a flow have some things in common. First, they have something that changes with temperature like a bimetal movement that moves an armature or flap when it heats up. When that piece moves it opens the port to a flow of whatever it is working with such as water or air. When it cools off a spring or just the flex of the flap closes the port again. Of course the operation can be inverted instead, so that it closes the port when it heats up and opens again when it cools down. I think this one allows a flow after it heats up and that opens the big air port to fresh air from the front of the car.
It's nice to know they never fail though, thanks for that. Someone was asking how to test the thermostat that's why i replied to that question. Note i am not saying it would definitely work just that it might work.

Snapping off nipples, wow, i'd hate to have that happen. Not sure how anyone repairs that other than maybe epoxy or something that can stick to the type of plastic the air box is made out of. I'll be more careful now when playing around with those v lines.

Thanks.

[454cid]

Hello,

I am not sure i made it clear what was being tested.
I was talking about testing the vacuum thermostat ONLY, not the entire system that controls the air box temperature.

The vacuum thermostat must be mechanical with a valve that opens and closes depending on temperature. The valve mechanism itself would not care if the flow was caused by a vacuum or a pressure, as long as there was a pressure difference...

...So what i was talking about was a simple test to see how the pneumatic thermostat worked ONLY in a fairly simple test to see if it worked at all and what temperature it starts to open and/or close at. It would not be as complete as a full system test because it may be hard to deduce intermediate states...

I think it would be very difficult to tell how much air the thermostat was passing. The aquarium pumps I have had, flow so little that it can be hard to feel, so unless you could rig up some sort of very low pressure gauge it might not provide much information and even then It would be hard to correlate that to the vacuum diaphragm moving the door, I think.

[454cid]

You can’t assume the thermostat operates the same on a pressure differential as opposed To designed working pressures without knowing more about the inside. Those don’t fail in our experience , it’s vacuum hoses and fitting ends that fail on this system, or snapping off the nipples with gorilla techniques

The rubber fittings fell apart on mine, and I wondered why Volvo used that hard nylon looking line. I wondered it it were a deliberate restriction as I assume it's a smaller internal diameter. The big malfunction with mine was the vacuum diaphragm keeping the door in the middle. As best as I could tell at the time, it was never fully open to fresh air.

[MoVolvos]

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Reinstalled the ABS Module today. After testing the repair I removed it to seal the top with high temp silicone and so far so good.

Remembered to take a look at the vacuum line and discovered that I had already found the problem and fixed it . Was getting dark so didn't take any pictures. I believe the photo was taken earlier and I didn't see the problem in the photo till a couple days ago thinking it was still there, forgetting I had found it later and made the repair .

Thanks for all those that assisted besides the vacuum diagram. Will link this to my Project Post so I can take a look at the other vacuum lines when time permits.

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[MoVolvos]

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Dried & old but workable.
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Vacuum Hose 1.jpg (482.41 KiB) Viewed 224 times

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[MrAl]

Hello,

I am not sure i made it clear what was being tested.
I was talking about testing the vacuum thermostat ONLY, not the entire system that controls the air box temperature.

The vacuum thermostat must be mechanical with a valve that opens and closes depending on temperature. The valve mechanism itself would not care if the flow was caused by a vacuum or a pressure, as long as there was a pressure difference...

...So what i was talking about was a simple test to see how the pneumatic thermostat worked ONLY in a fairly simple test to see if it worked at all and what temperature it starts to open and/or close at. It would not be as complete as a full system test because it may be hard to deduce intermediate states...

I think it would be very difficult to tell how much air the thermostat was passing. The aquarium pumps I have had, flow so little that it can be hard to feel, so unless you could rig up some sort of very low pressure gauge it might not provide much information and even then It would be hard to correlate that to the vacuum diaphragm moving the door, I think.

As we were talking so much about the aquarium air pump i forgot to mention what i ACTUALLY used for this test.

I used a 150mL syringe and some air tubing and two aquarium check valves, and a "Y" air tubing connector. You can generate air pressure OR a vacuum with that, and the vacuum is enough to draw the actual vacuum actuator in and open the flap inside the big port of the air box. You may also need a diameter reducing adapter for the syringe if it has a bigger nozzle than the air tubing will fit into. Some of these 150mL syringes have a bigger nozzle but often you can get them with the adapter included and a length of air tubing. You may be able to use a 100mL with no adapter.

The operation is simple. When you push the plunger in it pushes air out ONE of the check valves, but not the other, and that is the air pressure port. When you pull the plunger out, it draws air into the chamber through the OTHER check valve and not the previous, and that is the vacuum port. You get air pressure out of one port, and a vacuum at the other port. The check valves are what steers the flow.

To construct this tester, cut a short 3 or 4 inch piece of air tubing and connect it to the tip of the syringe. Connect the "Y connector to the other end. Now you have a syringe with two air ports.
Next cut two more 3 inch pieces of air tubing and connect them to the two open "Y" connector ports.
Next connect one check valve to one of the short tubings pointing in toward the "Y" connector, and the other check valve pointing out away from the "Y" connector.
To test, withdraw the plunger of the syringe and you should hear air rush into the chamber. After it is fully withdrawn, push the plunger back in and you should be able to feel a strong air current coming out of ONE of the check valves but not the other. That is the air release port and you would only use that for generating air pressure not for vacuum.
The other port with the other check valve is the vacuum port. You can connect some air tubing to that and to the nipple on the vacuum actuator on the air box. When you push the plunger in it is ready for the test, then when you pull it back out you should see the air flap move, and it should move quite a bit probably all the way. That tests the air actuator, although for a truly complete test you would have to have a vacuum gauge too and connect that with another "Y" connector, and get the spec for the car and compare.

The syringe is a regular syringe that is used for medical purposes and is 150mL although you may get away with smaller or larger.
It should be of decent quality of course.
All these parts are quite cheap to buy under $10 USD.
The Cheat Sheet is you can get away without the "Y" adapter if you push the plunger all the way in just before you connect it to anything for a vacuum test, but it will be a pain to operate if you have to do the test several times because you'll have to keep taking the tubing off so you can push the plunger back down for the next test. There is a chance you wont have to do that though if all the air joints are sealed perfectly so there is no loss during use.

As to the thermostat, you would have to connect this thing to the thermostat and heat that up and try to operate the vacuum actuator like that. At some point the thermostat should open enough to let the actuator move.
To test for 100 percent operation you would have to have the spec of the car vacuum as well as a vacuum gauge.

I dont know how i forgot to mention this i did it this way, except for the thermostat test never got to do that.