Whats that black flexible tube that comes out of the back of the valve cover (one on each side)... mine broke on the passenger side.

Also, what is the best source to buy a Factory Service Manual for a 95 Cab?

Thanks all!

 

Crank ventilation. I got 3/4 hose from some random place, and put it in as a substitute.

Not sure about the manual. I think Bentley.

 

you can re use the stock ends on generic hose

 

I call them goo tubes. Because they seem to have browninsh goo in them all the time. Last time I pulled the valve covers it appeared they were part of the crankcase ventilation system, I think they are Audi's version of BMW's "Oil Separator" valve which is supposed to vent crankcase air--separating oil-- into the TB. Likely the mesh in the valve covers gets gummed up and isnt separating--which is the brown goo slipping into the TB. Or the car isn't getting up to operating temp thus the water mixing with the oil.

 

Crank breathing tubes is correct. After about 15 years or so they become brittle and snap.
OEM price for the real deal is around $75 each or you can do as Luxus showed and make your own.

The ribs help to keep the oil out of the TB simply by introducing friction.

Not a 100% effective design, if you remove your TB you will find it baked with soot.

I pop mine off once in awhile and run cleaners through them even though I know it is only temporary.

 

Crank breathing tubes is correct. After about 15 years or so they become brittle and snap.
OEM price for the real deal is around $75 each or you can do as Luxus showed and make your own.

The ribs help to keep the oil out of the TB simply by introducing friction.

Not a 100% effective design, if you remove your TB you will find it baked with soot.

I pop mine off once in awhile and run cleaners through them even though I know it is only temporary.

 

The mesh material on the inside of the valve cover right where the goo hose nipple is, indeed serves a purpose. It is supposed to keep the oil out of the hoses. Since it isn't removable, next time the valve cover comes off, I will soak the cover in kero and try cleaning this out. I suspect if done properly, will help keep the oil out of the hoses?

 

It helps but oil still gets through just from pressure and vacuum.
I cleaned both my 90 and A6 covers and they were caked but it does eventually come back.
Not sure how long or how often you want or need to do this as removing the VC disturbs the gasket thus it should be replaced.

Without the mesh and ribs on the hose I would hate to see how baked the butterflies and IM would become.

 

I popped the mesh oil separator screens out of my valve covers because they were so gummed up. One winter they froze and the crank case pressure built up to the point where it blew the rear cam bore plug out of the head. I started running an oil catch can to catch the "brown goo", which I'm pretty sure is oil foam generated by the valve train. I bought the catch can on eBay for like 20 bucks. I have to empty it like once every two or three weeks. You'd be amazed at how much sludge gets stopped from going through the throttle body by adding this little catch can.

 

I have owned these off and on since the late 90s and this has always perplexed me. It is from water getting into the oil. This comes from two sources near as I can tell. One, the engine never gets warm, mainly from repeated short trips. Thus water builds up in the Crankcase. This issue could also be a bad thermostat not letting the engine get to operating temp. The other source is a failing head gasket. I think my cause was the latter on the last car. I had to add antifreeze every few months, not a lot, if I filled it to the max line on the filler, it would drop to maybe halfway between full and low over a period of three-four months. It wasnt leaking anywhere that I could see. It had to be a very minor head gasket fail somewhere. The goo would be on the inside of the oil filler cap in winter. That mesh material appeared to be non serviceable--all I could surmise was the water vapor passed though and some oil with it.
The fact that yours froze is further evidence to me this is an oil separator system like I have on my BMW 3.0 X5. Same deal. Short trips, water builds up and it freezes the valve, and the thing hydrolocks--all the oil goes into the tops of the cylinders. The first time it happened it was CPO but its a $1,000job. The second time I caught it before it "blew" and was outside with a damn hairdrier heating the valve to get the water out. BMW told me I have to drive the suv an hour a week on the highway in winter. Nice, huh? Should be a recall.
Anyway, this seems to be what that mesh is for. An oil separator. I am convinced now that those covers have to come off, and I have to clean that mesh--and ascertain that the car is getting to operating temp.