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Discussion Starter · #1 · (Edited)
Unlike the Audi TT Mk2 1.8, 2.0 or 2.5 liter engines, the 3.2 VR-6 (BUB) PCV is located inside the Valve Cover "hump" directly behind the oil cap. Inside that hump, you'll find the Cyclone Oil Separator (COS) and inside the COS you'll find the PCV diaphragm (Vacuum Valve). Unfortunately, neither the COS or PCV diaphragm are available as individual replacement parts, instead Audi will happily sell you the entire valve cover for around $425 (USD).

You can save yourself the cost and hassle by simply replacing the TT's vent tube with a Touareg PCV valve as described in this article from the Audi TT UK Forum -
OEM Audi TT Mk2 3.2 VR6 vent tube -
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OEM Touareg 3.2 VR6 PCV vent tube installed on the Mk2 TT -
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I just read the entire thread on ttforum and I have a question... When retrofitting the Touareg PCV, do you have to remove the original one under the valve cover or just leave it in there? Does a Touareg valve cover have anything in there, under its valve cover? I feel like keeping the ruptured one (or the un-ruptured one) in there isn't the correct approach.
 

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Discussion Starter · #3 ·
As shown below, the Touareg PCV vent tube has it's own diaphragm and vent tube. This is why installing it is a much better design and maintenance option than the one inside the TT valve cover.

You don't have to remove the original diaphragm inside the COS, but at some point it would probably be worth doing it when the valve cover has to come off.

Once the diaphragm fails, it will simply split or tear and air will pass through it and the Toureg PCV will take over. The broken internal diaphragm will no longer be under dynamic load, and since it's contained inside it's own chamber within the COS, it's not going anywhere.

Given the timing chain will probably need to be replaced at 150,000 miles anyway, the valve cover will have to come off then and the COS and failed diaphragm can be completely removed.

I'm not saying it's impossible that a small piece of the diaphragm could come loose and manage to get pulled into the intake manifold, but I suspect given the design and containment within the COS, the risk of such a failure is very low.
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But if the current one in the valve cover is still functioning as it should, isn't it unwise to just add the Touareg one without removing the valve cover one? Meaning, isn't a pair of PCVs on a system designed to run on a single PCV going to screw something up?
 

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Discussion Starter · #5 · (Edited)
I've put over 10,000-km on my TT with a functioning diaphragm in the COS and a Touareg PCV breather hose installed in the intake manifold and there's no difference in performance or function. And I'm frequently running on the German autobahn at speeds in excess of 125 mph.

The reason I installed the Touareg PCV now is in case the 15-year old diaphragm inside my valve cover fails - which at some point it will. When that happens, all I have to do is block off the vent hole in the valve cover and the Touareg PCV takes over.

If you're concerned about having two diaphragms in series at the same time, then put the the Touareg PCV in your boot along with a M4 x 5 screw to block the vent hole in the valve cover. If you have the handy VAG screwdriver in your tool kit you're all set when the time comes.
 
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