Interesting. Took the PCV off today, checked and cleaned it (all looked OK) and put it back.
The lower pipe connection was pretty loose so I presumed that was leaking and making the noise. I made sure it was really secure.
Wrong! Still honking.
Took it off and fitted my old one. No honking.
It actually has a small slit right at the edge of the diaphragm, but when I tested it (sucking and blowing!) it seemed airtight, so I think the case is holding it adequately.
Further investigating the "honker" I took it totally apart and found a 5th component! I had thought there were just 4 (upper and lower case, spring and diaphragm).
Behind (above when fitted) the main diaphragm is a small (15mm or so) diaphragm/valve made of orange silicone rubber.
If you peer in through the small vent at the top of the unit you should see a tiny lump, 2mm or so, of that rubber. It's a little retaining plug moulded into it that pushes through a small hole in the case.
Except on my "honker" you can't see it, because it's missing. Must have broken off, disappeared into the engine and been cremated!
So that little valve can move around, not as designed, presumably allowing the noise to be generated. What problems if any that causes I've no idea.
See attached photo. You can see a little lump inside the vent, but that ISN'T the normal lump of orange silicone rubber, it's a tiny bit of the stalk and a lump of Evo-Stik glue!
So I currently have one PCV with a dodgy main diaphragm (fitted) and another with a faulty secondary diaphragm (being glued into place for testing).
I could easily make one working unit from them, but I'll wait until the one I've ordered arrives and see what the components are like.
Hopefully I'll then mix and match to make one excellent unit and one serviceable spare and bin the rest.
Final comment (for now) is that having learned more about real/fake parts I can see that the "honker" isn't a genuine Audi part. I thought it was when I bought it.
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2003 D2 FL S8. Irish Green Pearl/Beige. Solar sunroof, auto-dim mirrors, electric rear seat functions and extended leather. Ski hatch retrofit. Aftermarket reversing camera. DVB-T and XCarlink now removed as redundant.
2016 Volvo V40 T5 Cross Country (4WD) with ALL the toys including adaptive cruise etc. etc. Osmium Grey with Blonde/Charcoal leather interior. Polestar performance "optimisation".
(Even rarer than a D2 S8!) Oh, and a brand new engine at just under 30,000 miles on the factory one!
Finally: gone, but not forgotten.....
1998 D2 PF S8. Agate Grey/Platinum. Every option (I think) except electric rear seats, Tiptronic steering wheel, ski hatch, towbar & dimming door mirrors.
e.g. Cruise control, NavPlus/TV, Bose, GSM, Xenons, Solar roof, Parking sensors, Alcantara/leather everywhere of course.
(internal dimming mirror added later)
1998 (very early) Ford Focus 1.8 Zetec; ABS/TCS, Heated screen/mirrors, Aircon. Added Auto-dim mirror, Leather seats, Trip computer, Cruise control, OEM Ford SatNav with CD changer.
And before that a lot of Rover 800s, a few oddities, a lovely Triumph Dolomite 1850HL with Overdrive and way back in my schooldays an Austin Seven aka Mini 850!
