What does the Tip coolant control valve do?
 

I know I have a bad coolant control valve on my 2000 S Tip. This is the valve that regulates the flow of coolant through the Tip heat exchanger. On my car I got a terrible hissing sound after driving in some warm weather. A guy from China answered my thread on another forum and pointed me toward the coolant control valve. I disconnected the vacuum line and tested it with my MityVac and the valve wouldn't hold a vacuum.

So I received my new valve from Pelican today and see that the valve is what's called "normally open" in other words it takes vacuum to close the valve. But I heard the hissing in hot weather so it seems like the car was trying to close the valve, which seems odd because you'd think that's when the Tip would need cooling the most.

It looks like the coolant valve is kind of a Tip fluid warming circuit, which I could understand in cold weather to bring the Tip up to temperature quicker.

Anyway if somebody can explain the theory of operation of this thing I'd like to know what it's trying to do, especially in hot weather.

Dale,

I sent you some info to your email address -- let me know if receive it (or don't).

Regards,
paul...

Got it. Thanks (again).

Here's the valve. With no vacuum connected the valve is wide open.

http://i19.photobucket.com/albums/b1...ntvalve001.jpg

Hook up some vacuum and the valve closes. It's a little hard to see the valve gate because it's white but it's closed.

http://i19.photobucket.com/albums/b1...ntvalve004.jpg

Closeup of the valve. Auf = Off? Valve is open though.

http://i19.photobucket.com/albums/b1...ntvalve007.jpg

The valve on the car looks identical. I haven't actually seen inside but with no vacuum the action lever is in the same position. I don't get it - seems backwards to me. How can coolant flow through the heat exchanger with the valve closed? According to the Porsche literature the car sends vacuum to the valve when it needs to cool the Tip fluid. The only explanation I can think of is that the valve is controlling a coolant bypass - not a direct flow to the heat exchanger. Maybe closing the bypass forces the coolant to go another way and thus to the heat exchanger.

I used the Google translator.

Open => Aufmachen (Auf)
Close => Zumachen (Zu)

I tend to agree with you -- I interpreted the info the same, that when vacuum is applied to the valve, it opens allowing ATF to pass thru the cooler. So with no vacuum, the valve should be closed (?) -- I'm confused also!

Sorry I can't help further.

Regards,
paul...

Might that be a bypass circuit? Closed forcing it through the radiators.

I confess to being a total bodger, which is basically someone who knows enough to be dangerous but has low standards when it comes to actually repairing things correctly. I did some checking and it seems that the nipple for the vacuum line is broken or cracked on the valve. The access to the hose clamps, etc looks pretty difficult for this valve. I unclipped the top part of the valve (the vacuum section) and the valve arm naturally moves to a middle position at that point. So now the valve is kind of half on, which is probably good enough for the way I drive (pretty easy with not much stop & go traffic). I'll get it fixed eventually when I need to take the car in for something else. If I have to, I'll reattach the valve top when the cooler weather arrives.