MP4.2+6.0

Yeah, I guess only using it for 30-40 years I better be careful... Including the 2000 C5 4.2 with the same valve, and the oil screen in the venter of the V below it under the access cover. Pulled all this stuff out and cleaned it up over the years while looking for a long running oil burning issue that motor had--which turned out to be internal motor.

Old stuff used to be a fair amount stronger than the enviro stuff they have sold for last 5-10 years. If it eats parts out like this that live in a harsh environment to start with, the right answer to me is buy a new part, not use a tired old thing prone to failure. Brake fluid also does way more a number on paint than brake or even stronger solvents. Zero issue with brake cleaner on factory painted brake finishes to be clear--D3, RS5 Brembos, A6 4.2 HP2's, etc. Not a good idea though for wheels as a contra example (or acetone, or toluene or ...)--or much of anything beyond about 409 or a degreaser if really necessary after a CV problem or something. More specific to part though, I would expect the rubber diaphragm here is pretty similar to brake component rubber, or a variety of other rubber parts found under hood or underneath. In each case, if rubber is deteriorating, it is more likely long term exposure to oils or something else that have started rotting it out. Plastic looks like ABS to me, which is really tough and resists all but a very few solvents. It does eat or crack some inside trim related plastics, but not a solvent I would ever use in interior anyway.

Panelhead

It may eat on mine. It has toluene, methanol, acetone, 2-butoxethanol, and methyl ethyl ketone. The contact time was a couple minutes. Sure cut the oil sludge. Eleven years worth.
I replaced the breather hose to the air box and the honking started. The old old had a broken retaining clip and may have been leaking. In a 2005 model this is another design flaw. You should not have to pull air box to change oil filter.

aTOMic

Got mine from FCP for $~30. Lifetime guarantee.
I disassembled my old one and "cleaned" it with CRC Brakleen (red can) and it disintegrated in my hands. Granted, it was the 150k miles old factory part - IIRC I had to cut one clamp off (it was one of those one-time use crimp clamps).
Note the picture looks different than the one on the car; the pictured part has a hose connection where mine had a vent. I called and after inputting the VIN the rep pulled one off the shelf and confirmed that for my car at least, the picture was incorrect.

jandreas

You just have to really pay attention to the makeup of the cleaners that you're using. Retailers in North America can pretty much market anything as "brake cleaner". Not everything is acetone but the local autostore variety type brake cleaners usually are. And the majority of plastics directly attached to the engine are actually glass fiber filled nylon which dissolves in acetone. MEK will do a number on the rest. There are less harsh solvents that do an equally good job without the potential hassle of destroying an expensive car part or the rubber/nitrile gloves you are wearing and the skin on your hands underneath...

aTOMic

Yeah but I am always so relaxed and happy when I use lots of brake cleaner in my (unventilated) garage! Those other cleaners just don't have the same effect!

Seriously, though, it's also the best wasp killer for the money. With the red tube on a can, you can shoot them out of the air from 20 feet! Instant death to the annoying bastages. We are plagued with red wasps and they are very aggressive.

BTW, you can put a like-new shine on most screwdriver handles with acetone; just dip repeatedly and let dry. The handles are frequently acetate.

What brand/product is effective for you? I'd like to find something that works yet has less VOCs.

seamore2001

Out of curiosity, anybody know the book on having an (indie) mechanic replace the valve and what's involved when one does?

Asking for no particular reason...

Panelhead

Labor may be less than an hour. I replaced hose clamps with screw type. Never haves like the VW type.

nathanwind

So I had replaced my crankcase breather about 2-years/15k miles ago with a brand new 077-103-245-B purchased directly from my Audi dealer (the original one had started 'honking' at that time). I actually had to return/swap my first purchase immediately as initially at install the brand new one was honking!

Low and behold yesterday it started honking again. Going to give a stab at taking it apart and cleaning it, but what gives with the failure rate on these? Shouldn't be a biannual replacement on these at a $120 price tag.

Brozee

I cleaned mine preventatively about two months ago. Be careful as the clips are brittle and I broke almost all of them. However it still stays together no problem. I'm still on my original PCV and i'm at 200k

aTOMic

Unreal! They don't make 'em like they used to!