turbo944

Okay, I'm replacing the reference sensors, heater hoses and a bunch more before reinstalling the intake (including the venturi delete and thank goodness, the big vacuum line that runs from the brake booster area was hard and seriously dry rotted!) and I read and saw the pictures of the Audi all metal heater valve, but I've seen only one picture which indicates a possible direction of flow and nothing else I've searched for here or elsewhere online (or at the auto parts store!) indicates anything and I'd like to be certain....

There is the high side and the lower down side where hoses attach to it and the direction that the vacuum line points. I am "assuming" that from the only picture I found of a 968 with it installed, that the low side and that same direction where the vacuum line points goes toward the engine and the vacuum source and that the high side goes toward the heater core...is that correct?

My thoughts on the operation of the valve are that under vacuum it pulls a plunger up on the metal rod I see running down the central tube that blocks flow up the central tube and it flows out the high side to the heater core. Right now obviously without vacuum on it air flows freely through from one side to the other, as it should if vacuum were to fail.

Thoughts please???? I know some of you out there have install these!!!! Maybe it doesn't matter which was as long as the plunger is blocking the flow?

Thanks!!!!! Hoping to have her together and bleeding the coolant and power steering on Friday!!!! Then I can make one GIANT post on the what did I do to my 944 today...that covers the last 3 weeks!

turbo944

Nobody????? Anybody???? I know you're out there!

Mangonesailor

Do you know which way the coolant is supposed to flow past the stock heater control valve? Because I have a theory:

If w/ no vacuum the valve flows freely, and with vacuum the valve is shut, then the valve is reverse-seated. Meaning the valve disk is on the bottom and the seat is on the top. The valve disc would seat better if coolant flowed into the bottom port and out of the top port. This leads me to think the bottom port is "in" and the top is "out." Thus, IMO, that's how it should be installed. The flow direction is from the block-->Valve-->heater-->block. So I would install it that way.

Anyone here have any ideas?

turbo944

Yes, both default to open without vacuum for the heater and that's where it is now. But with that shaft running all the way to the bottom, I'm guessing the vacuum pulls up something that blocks off the coolant flow there. Why there? Because the vertical part of the tube that runs past the inlet and outlet goes past the bottom part just far enough for something to be there that would block flow when vacuum is pulled on the top. Anywhere else doesn't make any sense to me, the vacuum is pulled at the very top and the easiest mechanical motion is a pulling up motion of a block valve which can't be between the two in the vertical lest it just block flow all the time, above and it would have to reverse direction in the top portion where vacuum is applied and that's complicated. Believing in the KISS principle for this item is where I'm drawing my conclusions from...that and a picture of one installed on a 968...

Mangonesailor

So, you think there's a cylinder on the bottom 1cm of the valve that's pulled up and blocks the bottom port when vacuum is applied?

Maybe you should buy another and cut it open to see how it operates. Or you could PM jerome951 or josephsc since they've done the same thing before.

turbo944

Ah....thanks, I may have to do that....alas, had the back speed/ref sensor break off the metal portion in the bracket...it's not in the bellhousing, just in the bracket...can see under it, but it won't come up through the rest yet (and no drilling where it's broken on top...broke a drill bit already! So something of higher priority is currently in play.

Thanks!

jpk

if there is no arrow indicating flow direction on the valve, I would think it doesn't matter.

turbo944

I kind of thought so as well, will let it linger and see if anyone says anything else. Would think that it would work right either way, just that one way there will be coolant in it all the time and the other it would be blocked before going into it. Shouldn't really matter, but if there is a specific way, it would be nice to know.

Thanks!