Thermostatic valve in air cleaner test

[mrbigmax]

@Gitchigumi
If you are talking about the little valve in the air cleaner, they can be found for a lot less than $100. The thermostatic valve has part no 113129828 A or equivalent 035129630B. They were used on 1980s-1990s water cooled VWs too.
http://www.germansupply.com/home/customer/product.php?productid=18319&cat=388&page=4
http://www.rockauto.com/catalog/x,carcode,1283262,parttype,5072

[wayne1230cars]

I could not get mine to work and so I obtained a new valve from German Supply @$28.00. It is identical to the old one and quite easy to change. There is a clip on the front of the air cleaner that you carefully pry off and the new valve just slips in from the inside of the air cleaner. It took me 5 minutes. Make sure you get the brass fitting on the correct side. I don't know how much of a difference it will make in engine warmup but I like things to work as original. Before you buy one of these valves, make sure the flap part in the air cleaner is working.[img]

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[Tim Donahoe]

I have a follow-up, too. I spliced the two tubes together and the warm-air flap opened all the way when I started the engine. So the flap works, using this testing method. So I need a new thermo valve ... which I will get at German Supply.

Thanks, everyone.

Tim

[Kodok]

Gitchigumi Wrote:

[Hyperspace]

I have a filter box in the garage, on which the litte wire arm, that actuates the flap, broke... Damn nut that keeps the chimney closed is stuck like a mofo though, so not repaired yet.
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[Weezle]

"Actually you can check it working by looking at this little indicator. It's an extention of the shaft holding the flap.

In cold weather it should be up at an angle. When the engine is warmed up or if the weather is warm, it should be horizontal (flap closed, carburetor sucking non-preheated air directly through the intake). "


I like this answer, thanks. Easy test.

[korfmach]

Someone disabled the vacuum circuit to my warm-air flap by removing the vac can and plugging both the supply and reference ports in the central idle tube junction. Does anyone know if there's an alternative routing for the hoses that will still allow the warm-air flap to work correctly?
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[Juanito84]

[Juanito84]

[Tim Donahoe]

Weezle has the easier way: just look at the center line on the small door-flap hinge pin.

The line will be horizontal when the flap is closed, and going toward vertical when the door is opening to allow warm-up air.

This hinge pin is about the size of a pencil eraser. It has a line in its middle. You can see it easily. It's right there in front of you.

Don't try this on a real hot day unless you do it in the cool morning. Start the car and see if the line in the hinge pin moves to the vertical position. That means the thermo valve is opening your flap/door.

Tim

[Juanito84]

Ya, either way should indicate the flap movement. I just perfer looking directly at it.

IMO, whether the flap fully moves one way or another or even moves at all is not what is important. What is important is that the air temperature inside the air cleaner be about 100º F at low loads, regardless of ambient temps. Of course if it's over 100º outside the flap shouldn't move much if at all. But even in cool weather, if the air cleaner thermostat goes bad and causes the flap to stay up it will be pulling 165º F or hotter air off the cylinder head if the engine thermostat is working. That's too hot.

At WOT the flap should lie back down cutting off heated air. As you can see, both temperature and engine load should affect the flap's movement.

Just my 1.5 cents.
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If a water cooled engine cools its water with air, isn't it just an overcomplicated air cooled engine?

[bluebus86]

I am tuning my motor, it is I think a 74 motor (its in my 61 Bug) It has the plastic air cleaner
I wanted to see if the hose that is connected to the intake manifold just below the carb is a source of a vacuum leak. sucking on it back to the aircleaner I found it dont hold vacuum.
The flap mechanism in the snorkel however does hold vacuum, the flap works fine when vacuum applied.

this lead me to the thermostat control unit, the one with the two hoses on it. I am not totally sure of its operation charectoristics. I have removed it, cleaned it, confirmed the ball valve is present and seals and also removed the brass outlet and found the rubber seal under it to be in nice condition, clean and flexible.

I also note a small drilling on the plastic body, possibly a vent.

When I suck on the hose from the intake manifold to the thermostat unit, this vent hole is a source of a vacuum leak. is this correct to leak from this small hole? should we assume this small vacuum leak, which leaks to the inside of the aircleaner is an intentional part of the design?

I also noticed that I think the amount that the brass pipe is screwed into the unit possibly effects the calibration, the more screwed in, the more the brass tube makes contact with the aforementioned little gasket under it.

at anyrate, can some one confirm or not if there is supposed to be a small vacuum leak from this unit on the port that goes to the hose to the intake manifold (I am testing at approximently 60F) ????

Not being framilur with this late VW aircleaner system I am a bit confussed, Normally any intake manifold leak is cause for concern, but from what I gather, this small leak might be normal part of operation of this thermo vacuum unit, Id like confirmation one way of the other.

Thank you

Keep Buggin!
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[Tim Donahoe]

I don't know al lot about the valve. When mine failed to open four years ago, I tried to clean and refurbish it, but I ended up buying a new one.

I seem to remember a bi-metallic spring inside the unit, and most of all, I remember that if the unit fails in the open position, it can be a source for a vacuum leak. This vacuum leak is often hard to find, since most owners don't realize that a faulty thermostatic valve in the plastic air cleaners can be the culprit.

If your valve isn't working, I'd just get a new one from RockAuto (the Rabbit ones are the same, so look under Rabbit for parts).

As far as the hole in the thermostat is concerned, I can't remember it's function exactly, but I seem to recall that it has something to do--at some point--with letting off pressure within the unit itself. So this hole may be the source for the vacuum leak I heard of when the unit does fail.

You can always plug the line, or the male nipple on the manifold, and see if your vacuum leak goes away. At the least, you'll know it's not the valve.

Tim
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[busdaddy]

It's been a few years since I dismantled one of those valves and studied them but I do recall it being much more complex than it outwardly appears.
Yes it does direct vacuum to the dashpot that opens the heat flap when it's cold in the inlet. And when it's finally warm enough it cuts off the vacuum and allows air to return through the hose to the dashpot so it can close.
But I seem to recall it also becomes a pseudo idle compensator when it's warm by creating a vacuum leak and leaning the mixture slightly.

There should be no vacuum leak on the manifold port nipple when it's below the opening temp marked on the housing (usually ~90*F). The rubber seal on the end of the bimetal strip is likely petrified.
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[bluebus86]

has a small leak thru the vent hole when warm, but not after I frooze it via the tiny hole in the body of the unit once warmed up, the hole is what allows the vacuum to be released allowing the hot air flap to return to warm running position. so yes the unit does have a pin hole leak when warmed, and it needs that leak to release the flap to return to warm position.

Its ok, mine is working.
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Stop introducing dirt into your oil when adjusting valves ... https://www.thesamba.com/vw/forum/viewtopic.php?t=683022

[Tim Donahoe]

The easiest way to test the air cleaner thermostatic valve on the paper-element air cleaners is this:

Make sure the ambient temperature is under 70 degrees Fahrenheit. Look at the air cleaner snorkel, and you will see a small hinge pin (my wife is pointing at it). Start the engine, and look at the pin. If cool enough outside, the line in the hinge pin will move to the vertical. This means the flap on the snorkel has opened to allow for pre-heated air o enter the air cleaner.

The thermostatic valve will operate the snorkel flap anywhere between full open and full closed, according to the ambient temperature.

If the line on the hinge pin stays horizontal on cold morning start ups, then your thermostatic valve is shot, or your vacuum is not hooked up correctly.

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[APPLEGREENVW]

[Boble]

Curious about what's inside this fella, I cut one open some time ago. As you can see below, there are TWO valves inside:

1. A piston valve that controls the vacuum flow to the air filter flap

2. A ball valve that opens up when warm and thus "zero'ing" the vacuum.

There are "no serviceable parts inside". If it don't work it's probably just dirt in there. Soak in solvent and blow though it with compressed air. Test with cold air (fridge) and warm air (hair dryer).

[APPLEGREENVW]

Boble
How do you adjust your thermostatic valve?
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02/76 Beetle sedan

[Boble]

Hi,

The piston valve that actually controls vacuum to the air filter is not adjustable.

The ball valve is, though.

You want it to open at around 77 F (25 Celsius). I think your description above makes sense. Like this:

1. The whole unit should be at 77 F (25 Celsius). Give it enough time to reach that temp
2. Block the piston valve tube (brass) and the "small bleeding whole" beside the ball valve screw on top
3. Suck on the plastic tube with your mouth
2. Adjust the ball valve screw until you find the point where it just opens

I cannot believe that it is super critical if you don't hit exactly 77 F, after all it just regulates the air temp to the carb.