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The flaps direct the air....

ok, maybe I need a picture...

are these flaps on the top? under the main cooling tin? like the one that sits on top of the oil cooler

if none of the heating stuff is there will these still be?


I know I'm still a babe in the woods on this, but this is REALLY making me feel dumb!

on the top of the motor right behind the cooling tin around the fan should be a cross bar that pivots. it is connected to directional flaps withinthe cooling shroud. you can push on the cross bar and hear the flaps open and then close when you let it go.

OK In the Haynes bus manual (72-79) page 23 ..parts #: 42, 45...those are the flaps.
In the Haynes 914 manual: Page 22 parts # 42 and 45
In the Haynes 411/412 manual: page 21 parts # 42 and 25

Look at all the other parts attached to it as well. Ray

ok, I see now... I KNOW (99% sure) I do not have piece #42 , but I think I have piece #45, not sure though... if these are gone, will my engine run hotter? what should I do?

Keep in mind when refereing to engine sides (left/right) we have both bus owners, and 914 owners here, since th 914 motor is mounted "backwards' in relation to the Bus, we might get confussion in reading these posts (I know I am confussed here)

Might be best to refer to 1/2 side, verse the 3/4 side (cylinder numbers) so we all know what everyone is talking about.


My understanding is that if the thermostat fails by leaking at the bellows, or breakage of the wire, the two flaps go to the defualt full cool postion, so there is no need to worry about over heating for these two failures.

Warm up can be important, as an engine that spends more time not warmed up, may experience more wear. In cold climates, or if used for short trips, this can be more of an issue.

on side 1/2 the flap is down when cold (blocks air), and turns up and out of the way when the thermostat warms up, thus allowing full cooling air to fins. On 3/4 side the flap is up when cold to block the air, and down when warmed. The 3/4 side flap is hinged on top, on 1/2 side the flap is hinged at bottom, via a linkage.
If flap is missing on side 1/2 little differnce would be expected verses if flap was there, and in the warmed up position. On side 3/4 I believe from looking at it, that is flap is missing, the ratio of air to the oil cooler, verses air to the fins will be altered, as the flap when down (warm position) serves to direct a certain amount of air to the oil cooler, lack of the flap would proabably send more air to the oil cooler, at the expense of air to the fins on that side (this is my assumption, no hard data,)

I gather from one poster that flap 3/4 was cut to allow more of the air to go to the oil cooler, is this correct? and if so, wouldn't that robbing air to the fins, to give to the cooler? If thats the case, i'd perfer adding an external oil cooler with electric fan rather than rob fin air on that side. the heads probably need all the air they can get, and i'd have concerns about one set of heads running at a much different temp than the other side.

It was also stated that removeing soem lower tin pieces improves air flow, does anyone have hard data on this?, and which pieces were removed?

Also note on 914's, later years had two small plastic flaps added to the underside of the car body, just below the fire wall. It was stated to me this was added for imporved cooling, I assume it creates a vacuum behind them when car is at speed, which in turn assists the exit of air from under the engine (in essence, helps draw more air out to under the car) This to me makes sense, as the underside of the moving car is likely under pressure.

What is the effect on life of the alternator is cooling duct to it is blocked? I assmue VW added the alternator duct for good reason, so give better alternator life.

At anyrate, add the fire wall plastic flaps if you do not have them on the 914 (easy to do)

Awaiting info on what tine to remove on underside, can someone please confirm?

On a bus shroad the cooling duct to the alternator is not affected by the flaps since it is down in the shroad. We also have 411/412 owners here.

Dave M. The flap system is very misunderstood by about 90% of all who look at it. I may not have been clear in the flap operation. When the flap on the 1/2 side is closed...meaning blocking the airflow to the cylinders....the 3/4 side when operating properly is also lifted. It only partially blocks the airflow to the cylinders. But, because the part of the plate that protrudes into the fan housing has a very sharp down turn, this flap position also cuts off a bit of the oil cooling air flow.

When the flaps are full open...meaning the 3/4 side flap is on its runners or rest area....seemingly covring the oil cooler opening....the cooler is actually getting full air flow. Look carefully at the ducting. You can only do this by splitting the fan hosuing open. You will notice that the 3/4 side cylinder opening is actually much larger than the 1/2 side. That is...until you install the 3/4 side flap on its hinge pins. Then the opening is nearly the same as the 1/2 side. The flap bisects off a portion of the duct to use as its own. There is no way to "rob" cooling air from the cylinders...unless you physically block the duct. What I am playing with is trimming some of the dwon turn to give the onrushing air from the fan more of a straight shot to the cooler...without adding a duct into the cylinder airstream. The main problem with low cooling velcoity on the 3/4 side is that people comonly install the plate/lever link incorrectly (part #44 in the diagram in the bus book). If installed incorrectly it causes the plate to open all the way when it should be closed. In this position is gets reduced airflow to the cylinders...but actually gets quite a lot to the cooler, due to the air rolling over the lip. In this respect you can be running respectable oil temperatures....and still burn up the 3/4 cylinders. Also the large volume on the 3/4 fan side reduces velocity over the cylinders compared to the 1/2 side.

Of course, to make this work, I need a little better airflow on the 3/4 side anyway. The problem with the cooling fan housing is all of that excess space on the left side. Split the manifold and look at it carefully. This becomes obvious instantly. There are large air traps and a longer distance for the cooling air to flow on the 3/4 side. It has reduced velocity. I am reducting slightly inside to make it more similar to the right. It gives a shorter more direct path to the opening.
In the long run, I most likely will delete the original cooler. I have just been thinking about that lately. The stock VW cooler is actually very efficeint in its design. For the relative amount of plate and fin area...its a good deal more efficient than your average mesa type stacked plate cooler. Its just small. I will be using a pair of them...mounted on Audi 5000 type adaptors. They will be cooled by a single fan and the pair of them hung, stacked, behind the sheet metal behind 3/4 by the bell housing.
The audi adaptor uses the original oil cooler seals, but has a hose fitting on the other side. I will plumb to flow oil in one cooler, exhasuting inseries into the next...with a tight duct and small fan. I will pull the oil from the original oil cooler mount...through the two block offs right above the holes. I will use a block off plate to plug the origial oil cooler holes. this takes one more 90* bend out of the system. The oil reenters teh same galley as the origial oil cooler did. I will use a take off from the return cooled oil line to feed my rocker and piston oilers

The duct hole to the alternator makes these things cool extremely well.thats why they last forever. They are cooled backwards from a fan type. The cooling air pushes from teh back and exhausts into the engine compartment. I may try installing a motorola type fan driven one. But to do that, I will be building aduct cover for the fan and pulling the air from the cooling intake boot on my 412. To disconnect the original cooling boot on a type 4...you must be able to install a fan and then have a source of air other than hot air from the sealed engine compartment to pump through it. Sorry for the length. Ray