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First-time Eurovan owner, vacuum lines and center vents
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hellogoodbye
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PostPosted: Sat Jun 08, 2019 7:22 pm    Post subject: First-time Eurovan owner, vacuum lines and center vents Reply with quote

Hello everyone!

Finally, I have purchased my first VW, a 2002 Eurovan GLS (or GL?). It doesn't have table or anything and all the seats face forward.

170k miles. Seems very well maintained, and I have a good mechanic I think who can help me out.

So, one issue we started to diagnose which we have not solved quite yet.

While driving with auto AC on, when I step on the throttle anything more than gently, the center vents cease to blow hardly anything, and a rush of air is directed to the far left and far right vents. It's discussed quite a bit in the VW Vortex thread: https://forums.vwvortex.com/showthread.php?5640499-2002-Eurovan-A-c-vents-roar-when-pressing-the-gas

Some troubleshooting was done. We checked the little half-blue/half-black one-way valve. It seems to work in the sense that it restricts flow one way, but not entirely, and in the other direction it lets air through without restriction. Correct? Or should it not let any air through via a specific direction?

With that out of the way, I discovered that if I eliminate the white tee-fitting and associated black/white braided line just next to it (circled red) from the blue vacuum tubing line, and just have a straight shot of blue vacuum tubing with the plastic black/blue 1-way valve (thus following the blue line only), the problem goes away.

This red-circled section that tees off goes to a blocky metal valve (lower right, within the red circled area) or something, which then heads down into the depths of the engine bay. See photo below.

Image may have been reduced in size. Click image to view fullscreen.

Any idea of the function of that braided line which tees off the blue tubing? Can I leave it disconnected and have my vents functioning okay? Bad idea?

Thanks!!


Last edited by hellogoodbye on Sat Jun 08, 2019 7:52 pm; edited 1 time in total
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Abscate Premium Member
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PostPosted: Sat Jun 08, 2019 7:52 pm    Post subject: Re: First-time Eurovan owner, vacuum lines and center vents Reply with quote

Just get a generic check valvefrom your FLAPS and replace the one that’s leaky
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hellogoodbye
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PostPosted: Sun Jun 09, 2019 4:39 pm    Post subject: Re: First-time Eurovan owner, vacuum lines and center vents Reply with quote

I'm definitely ignorant of a lot here...

FLAPS?

And you mean the black/blue valve in the photo should definitely not pass any air in one direction?

Thanks!
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PostPosted: Mon Jun 10, 2019 2:48 am    Post subject: Re: First-time Eurovan owner, vacuum lines and center vents Reply with quote

Friendly local auto parts store , sorry

Yes, a check valve should blow clear one way, and no flow the other.

When you step on the gas ,manifold vacuum drops and that is messing up your AC
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hellogoodbye
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PostPosted: Wed Jun 12, 2019 4:39 pm    Post subject: Re: First-time Eurovan owner, vacuum lines and center vents Reply with quote

Well, I checked that valve again. Seems okay actually. Also double checked that it's oriented the right way, with blue side on intake side, meaning the air gets sucked thru the blue section first, then thru the black section.

I wound up moving the tee fitting to the opposite side (black side) of the check valve.

It fixed the issue but I don't know if it actually fixed it, if you get my drift. Maybe something is non-functioning or possibly getting damaged in the process? Front AC still works, no dash lights...
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Stripped66
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PostPosted: Wed Jun 12, 2019 8:39 pm    Post subject: Re: First-time Eurovan owner, vacuum lines and center vents Reply with quote

Your diagnosis was spot-on the first time; the check valve works as it is supposed to.

Inspect the N147 solenoid, the hoses running to and from the solenoid, and the coolant cut-off valve (it has a vacuum pod that opens/shuts the valve).

On the N147 solenoid, the vacuum hose from the tee is running to the correct fitting. There should be a vacuum hose connected to the barbed fitting perpendicular to the inlet, I've circled this in yellow (...I cannot tell from your pic whether there is a hose connected to this or not); this hose should run to the vacuum pod on the coolant cut-off valve. If there is no hose on this fitting circled in yellow, but instead the hose is on the fitting on the back-side of the valve (e.g. running in-line with the inlet, not perpendicular), then that's your problem. If there is a hose in the correct location, then check whether it is running to the vacuum pod, and whether the hose or the vacuum pod holds a vacuum.

Image may have been reduced in size. Click image to view fullscreen.

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66brm wrote:
Bodacious wrote:
Why not just make a custom set of wires with a Y splice in them. Then you could just run one distributor.

I don't think electrickery works that way
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hellogoodbye
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PostPosted: Thu Jun 13, 2019 2:00 pm    Post subject: Re: First-time Eurovan owner, vacuum lines and center vents Reply with quote

I checked the line on the valve you circled, and it connects in the perpendicular fashion. It's by way of a short 2" section of braided tubing which transitions to a long skinny section of plastic tubing that routes down into the depths of the engine bay, under the engine down by the skid plate almost. I can't actually see where it goes. Is that correct? It's clearly attached to something but I can't see it.
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Stripped66
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PostPosted: Thu Jun 13, 2019 5:05 pm    Post subject: Re: First-time Eurovan owner, vacuum lines and center vents Reply with quote

Sounds correct...I'm guessing you have the belly-pan underneath the engine? The coolant cut-off valve is on the driver's side, low in the engine bay behind the radiator. Do you have a Mity-Vac, or some other way to pull a vacuum, to check where the leak may be?
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66brm wrote:
Bodacious wrote:
Why not just make a custom set of wires with a Y splice in them. Then you could just run one distributor.

I don't think electrickery works that way
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hellogoodbye
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PostPosted: Thu Jun 13, 2019 8:21 pm    Post subject: Re: First-time Eurovan owner, vacuum lines and center vents Reply with quote

Yes it has the belly pan. I'll look into finding the vacuum pod that the line running down into the engine bay allegedly attaches to.

But can you tell me why the temporarily eliminating the line related to the coolant cutoff valve would impact the air vents? Is it because the vacuum system is then rid of that leaky line, and can hold vacuum? I guess I effectively determined that something on that coolant cutoff is indeed the culprit correct?

Secondary question: as a test I put the tee fitting and braided line on the black side of the blue/black check valve and it fixes the issue. But maybe that's incorrect or a bad idea...?
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Stripped66
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PostPosted: Fri Jun 14, 2019 10:32 am    Post subject: Re: First-time Eurovan owner, vacuum lines and center vents Reply with quote

hellogoodbye wrote:

But can you tell me why the temporarily eliminating the line related to the coolant cutoff valve would impact the air vents? Is it because the vacuum system is then rid of that leaky line, and can hold vacuum?

Yes. The vacuum signal comes from the intake manifold when at partial/low throttle positions (high manifold vacuum). When you open the throttle, manifold vacuum decreases, at least below what's needed to keep the vacuum pods in the dash set to the necessary position. The vacuum reservoir helps maintain constant vacuum to the HVAC despite changing intake manifold.

But, since you have a leak somewhere south of the tee in the vacuum circuit, the vacuum stored in the reservoir bleeds off until there is not enough remaining to hold the HVAC vacuum pod in position, causing the flap to divert airflow away from the center vents.

Quote:

I guess I effectively determined that something on that coolant cutoff is indeed the culprit correct?

Yep, now exactly which component is the culprit is another story. Without a vacuum pump, you could still trouble-shoot the issue by plugging vacuum line or joining vacuum lines to bypass the solenoid, etc until you isolate which combination causes the vacuum leak/drifting HVAC flap to return.

Quote:

Secondary question: as a test I put the tee fitting and braided line on the black side of the blue/black check valve and it fixes the issue. But maybe that's incorrect or a bad idea...?


Meh...Somebody might spend a full page arguing with you about how this will affect the coolant cut-off, but it is doing they exact thing right now as it was when it the vacuum lines were connected as they were supposed to...the vacuum leak is still there and the cut-off is exposed to the same vacuum fluctuations as it was before. So, understand it's not fixed, but in the time being you've stabilized your HVAC vent position.
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66brm wrote:
Bodacious wrote:
Why not just make a custom set of wires with a Y splice in them. Then you could just run one distributor.

I don't think electrickery works that way
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cmazola
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PostPosted: Thu Jun 20, 2019 4:17 pm    Post subject: Re: First-time Eurovan owner, vacuum lines and center vents Reply with quote

I'm having the same issue, and its driving me mental. I had my heatercore replaced last year, and this all started then. Unfortunately I don't trust the shop (VW Indy who does tons of EVs) to take it back and fix what they messed up.

Hopefully mine is not a vacuum leak at the HVAC system... that will be pretty hard to get to.

Keep us posted.

Also, the coolant cutoff valve, does it have anything to do at all with vehicle cooling? if so that could also explain my overheating problem. Crying or Very sad
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Stripped66
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PostPosted: Fri Jun 21, 2019 5:25 am    Post subject: Re: First-time Eurovan owner, vacuum lines and center vents Reply with quote

cmazola wrote:

Also, the coolant cutoff valve, does it have anything to do at all with vehicle cooling? if so that could also explain my overheating problem. Crying or Very sad


It *shouldn't*. The valve affects coolant flow in the return loop of the heater circuit, and the coolant from the radiator ultimately goes to the engine whether that valve is open or closed.

I'd check the usual suspects (water pump, t-stat, radiator and leaks) before I'd suspect the coolant cut-off valve.
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66brm wrote:
Bodacious wrote:
Why not just make a custom set of wires with a Y splice in them. Then you could just run one distributor.

I don't think electrickery works that way
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Smithers166
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PostPosted: Mon Aug 30, 2021 10:03 am    Post subject: Re: First-time Eurovan owner, vacuum lines and center vents Reply with quote

I'm trying to track down the source of my center vents closing. I have replaced the check valve twice and I have blocked off the t where it goes to the solenoid under the brake booster. I was just replacing the plugs and figured I would try a different vacuum source so I moved the T to down below the engine at the air pump. It is a good source of vacuum but I still have an issue. I think I can say for sure that it is in the cab but don't know where to start.

Any thoughts?
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volkybus
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PostPosted: Fri Sep 24, 2021 7:56 pm    Post subject: Re: First-time Eurovan owner, vacuum lines and center vents Reply with quote

My defroster valve doesn't work at all. No. Matter the position of the control. Does anybody have a diyagram of the vacuum. lines?. Thanks Bill 93 Eurovan Mv/weekender, auto, changed to 5 speed
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