PCV valve and oil cap vacuum

[04lss]

Hi all,

My s4 has mostly sat in limbo for the last year or so while ive tried to figure out if i would sell it or not this spring. I have mostly decided to keep it. I drove it for the first time in a while tonight came home thought i heard whistling, but didnt. It got me thinking about the PCV. I pulled my dipstick and could hear air sucking in. same thing (to a lesser extent) for the Oil cap. I recall that this is a sign of a failing pcv. So the question is, how much vacuum is too much and a sign that i need a new PCV? I dont really drive the car that much so monitoring oil consumption may not be the best trick. Or maybe i just have plenty of time.

Car is e40 dual pulley so when i do drive it, Im not exactly gentle.

[Smac770]

You don't say what engine code or what model year you have.

The B8.0 3.0T crankcase vacuum at idle, set by the PCV unit, was 30 mbar originally and then 150 mbar revised. If you are 8K0907551 A or B, you should be running the 30 mbar unit. If you are 8K0907551 D 0003 or later, you should be running the 150 mbar unit.

B8.5 3.0T had the 150 mbar PCV from the start.

[04lss]

You don't say what engine code or what model year you have.

The B8.0 3.0T crankcase vacuum at idle, set by the PCV unit, was 30 mbar originally and then 150 mbar revised. If you are 8K0907551 A or B, you should be running the 30 mbar unit. If you are 8K0907551 D 0003 or later, you should be running the 150 mbar unit.

B8.5 3.0T had the 150 mbar PCV from the start.

I have a 14 b8.5, so it should be the later revision are those values i should be measuring? My understanding was that if i hear air sucking, the valve might be bad.

[Fresh.S4]

You don't say what engine code or what model year you have.

The B8.0 3.0T crankcase vacuum at idle, set by the PCV unit, was 30 mbar originally and then 150 mbar revised. If you are 8K0907551 A or B, you should be running the 30 mbar unit. If you are 8K0907551 D 0003 or later, you should be running the 150 mbar unit.

B8.5 3.0T had the 150 mbar PCV from the start.

Hey I sent you a pm the other day..
If I'm running 003 software and I'm pretty sure the earlier version PCv. So I should change huh?

[SwankPeRFection]

I have a 14 b8.5, so it should be the later revision are those values i should be measuring? My understanding was that if i hear air sucking, the valve might be bad.

There will always be vacuum on the dipstick tube and on the oil cap. You don’t want positive pressure in there.

[Smac770]

I have a 14 b8.5, so it should be the later revision are those values i should be measuring? My understanding was that if i hear air sucking, the valve might be bad.

Put a vacuum gauge on the dipstick tube, idling it should show ~150 mbar (4.4 inHg). If it's more than that, the PCV regulator valve is likely torn and allowing too much vacuum past. This risks the various seals on the engine. If it's less than that, meh, could be whatever. But you should not see it positive pressure (get a mixed pressure/vacuum gauge if looking to confirm that), except maybe just barely and just briefly at WOT.

I don't think an unmetered air leak is going to be as much a problem on a 3.0T as the 2.0T because the 3.0T is MAP driven rather than MAF driven. One guy didn't even have the breather line from the crankcase to the air intake path connected, just hanging there. So if you're hearing what you believe to be errant noise, you need to figure out what that actually is first. Not sure you can presume anything until the specific manner of noise is determined.

[Smac770]

Hey I sent you a pm the other day..
If I'm running 003 software and I'm pretty sure the earlier version PCv. So I should change huh?

Aye, it's "in the stack". According to the TSB https://static.nhtsa.gov/odi/tsbs/20...81642-0699.pdf if you're rev D and version 0003 or later, the ECM software is expecting 150 mbar.
C > F > Q > AC is the 30 mbar line
H > S > AB > AH is the 150 mbar line
For some reason, I recall there being more to this; it's probably in some thread some some time back here in this forum somewhere.

There's also the regulator diaphragm repair kits from Audi. That's nice of them.
06E103772G - not sure the application, is this for H and S, or for AC?
06E103772H - for AB and AH

Technically, the vacuum level is set by the spring and diaphragm, so I wonder if you could just use a 772H on a 547AC and effectively get a 547AH.