NORMAL CRANKCASE VACUUM

[Theiceman]

since pcvs and crankcase vacuum come up a lot, i thought i would take a snapshot of normal for reference. I think it may help the community out when troubleshooting pcv or oil leak issues. 2014 2.0T ( white top pcv) complete engine rebuild 10k miles ago. Running flawlessly.

2.9 inHG at idle warmed up..20200701_171418.jpeg

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[Smac770]

That's what old guy and I were also showing. I have white cap also; I believe he does too.

[old guy]

Perfect! Spec is 2.5 to 3 inHg.

[stelvio]

2013 A4 - white cap PCV
This is what the gauge looks like when connected to the dipstick tube at idle. I still haven't gotten a chance to look for caps to do a test at the Intake Manifold

[Theiceman]

2013 A4 - white cap PCV
This is what the gauge looks like when connected to the dipstick tube at idle. I still haven't gotten a chance to look for caps to do a test at the Intake Manifold

i might need a degree in aeronautical engineering just to read that gauge .. what does it tell you ? i really have no idea .. what is it reading exactly ??

if it is reading cm Hg should that not be reading about 7 at idle ? it should be reading more or less the same as mine right ?
maybe i dont know how to read it .

or are you showing us you have a vacuum leak ?

[old guy]

Here is the same gauge showing ~2.4 inHg at idle. The inner ring shows vacuum from 0 to 25 inHg.

[Theiceman]

ahhh now i see.. and the outer ring shows cmHG vac .... which shows about 6 .. thanks ..

[old guy]

ahhh now i see.. and the outer ring shows cmHG vac .... which shows about 6 .. thanks ..

Yep.

I am curious as to why Stelvio is showing almost no vacuum on the block.

[morris39]

since pcvs and crankcase vacuum come up.i thought i would take a snapshot of normal for reference. I think it may help the community out when troubleshooting pcv or oil leak issues. 2014 2.0T ( white top pcv) complete engine rebuild 10k miles ago. Running flawlessly.

2.9 inHG at idle warmed up..20200701_171418.jpeg

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For ref only. On MY15 S3 2.0 TFSI vacuum at idle reads 3"Hg. Under load 1"Hg @ 2000 rpm. In both cases vacuum is not rpm sensitive and the readings do not fluctuate. The gauge is not damped. No DTCs, car runs w/o any problems, 32 k miles.

[stelvio]

Yep.

I am curious as to why Stelvio is showing almost no vacuum on the block.

Same. Intake Manifold test(?) or is there something else I should look at? I am strongly considering replacing the entire PCV with a new OEM unit.

[old guy]

Same. Intake Manifold test(?) or is there something else I should look at? I am strongly considering replacing the entire PCV with a new OEM unit.

I also have a 2013 with a white top. If yours is the original it is probably a "J" or "AE" revision. I would recommend replacing it with the latest "AK" revision. I replaced mine at 50k miles as a preventive maintenance and plan on doing it again at 100k (if not sooner).

[Theiceman]

I also have a 2013 with a white top. If yours is the original it is probably a "J" or "AE" revision. I would recommend replacing it with the latest "AK" revision. I replaced mine at 50k miles as a preventive maintenance and plan on doing it again at 100k (if not sooner).

i think it money well spent every 5 years or so.

its odd people will pop coils in like they are candy but seem to resist putting a PCV in.

[Der Konig]

Thats a cool idea, gauge hurts my head though. I imagine the person that designed that had to do some crazy cross checking to get all the numbers right. Ill check mine out when I get a chance.

[B6_Dolphin]

I also have a 2013 with a white top. If yours is the original it is probably a "J" or "AE" revision. I would recommend replacing it with the latest "AK" revision. I replaced mine at 50k miles as a preventive maintenance and plan on doing it again at 100k (if not sooner).

I also replaced my "white top" PCV as preventative maintenance @ 47k miles on my '15 AR with the AK revision PCV.

[Buckyoufuddy]

Perfect! Spec is 2.5 to 3 inHg.

And what does a problem/failing PCV reading look like?

Low vacuum or high?

[Smac770]

Probably depends on how it fails. The PCV connects the intake manifold to the crankcase. Could it bleed high pressure from a boosted intake manifold? Sure. Could it bleed high vacuum from an idling intake manifold? Common. Could it cut off all pressure deviation from the crankcase? Maybe.

[snaky69]

Probably depends on how it fails. The PCV connects the intake manifold to the crankcase. Could it bleed high pressure from a boosted intake manifold? Sure. Could it bleed high vacuum from an idling intake manifold? Common. Could it cut off all pressure deviation from the crankcase? Maybe.

Who makes the OEM unit? Vaico? Uro?

[old guy]

Who makes the OEM unit? Vaico? Uro?

My OEM was manufactured by Hengst.

[Der Konig]

My OEM was manufactured by Hengst.

same

[stelvio]

My OEM was manufactured by Hengst.

same

same

[stelvio]

Also, FWIW, after replacing my PCV with an OEM one from FCPEuro [#lifetimewarrantythings] it seems my vacuum is back to normal.
Hopefully this can help others in the future.

[Novarider]

I'm gonna go pick up one of those black gauges from harbor freight, how are you connecting it to the dipstick tube?

[Theiceman]

Also, FWIW, after replacing my PCV with an OEM one from FCPEuro [#lifetimewarrantythings] it seems my vacuum is back to normal.
Hopefully this can help others in the future.

Great to see this thread was helpful on how to troubleshoot pcvs rather than" if in doubt swap it out"
Also great to see the different gauges and how to read them.

All I have to master now is checking the spelling in my titles before hitting send :(

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[stelvio]

I'm gonna go pick up one of those black gauges from harbor freight, how are you connecting it to the dipstick tube?

Kinda just keep it jammed in there a bit; it does not actually fit inside the tube but you'll figure it out.

Great to see this thread was helpful on how to troubleshoot pcvs rather than" if in doubt swap it out"
Also great to see the different gauges and how to read them.

All I have to master now is checking the spelling in my titles before hitting send :(

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Very much so; while the diaphragm seemed to be perfectly fine, it would appear another internal component of the PCV decided to let go so I'm glad I replaced the whole unit as it was not OEM, no idea when it was last changed, and lifetime warranty always helps.

[Novarider]

Just wanted to say thanks for making this thread.

I purchased the gauge from harbor freight and my pcv was only making about .5, the gauge barely moved. Replaced the diaphragm and it actually made it go into the positive! I quickly shut the engine off and ordered a genuine pcv from fcpeuro. Got it installed yesterday and it's now making 2.5 like it should.

I connected the gauge with a piece of vacuum tubing. It was just large enough to cram into the dipstick tube and make a decent seal. On the gauge side I used the metal cone connected to the tiny hose the gauge came with, it's just wide enough to shove into the vacuum tubing. Worked great.

Pcv's go bad so often and we get so many questions about it this thread should be a sticky.

[Theiceman]

Just wanted to say thanks for making this thread.

I purchased the gauge from harbor freight and my pcv was only making about .5, the gauge barely moved. Replaced the diaphragm and it actually made it go into the positive! I quickly shut the engine off and ordered a genuine pcv from fcpeuro. Got it installed yesterday and it's now making 2.5 like it should.

I connected the gauge with a piece of vacuum tubing. It was just large enough to cram into the dipstick tube and make a decent seal. On the gauge side I used the metal cone connected to the tiny hose the gauge came with, it's just wide enough to shove into the vacuum tubing. Worked great.

Pcv's go bad so often and we get so many questions about it this thread should be a sticky.

nice work .
i keep it handy now and just share the link for newer people coming on. of course it doesn't cover all failure modes as pointed out, but its a start.

[Chillaxin]

I had heard a slight whistling that would change pitch under boost (sounded like a/c refridgerant moving in a home air handler). Ended up doing this:

Replaced with latest AH. I found a decent amount of oil in the connector from the PCV/Combi to the Pre-turbo hose. Upon test drive, no longer had the slight whistling and low end power (butt dyno, possible confirmation bias) below 2500rpm had increased.
I hadn't seen this shared, so:


Just need a T30, some cleaner+rag for the gasket surface, maybe a magnet, and a torque wrench. Takes about 20min max. For anyone that is DIY, make sure to remove all the screws before you remove the PCV. Accidentally dropping them in the engine would be a nightmare. Hose connectors are quite easy, just take your time with them. I re-oiled the o-rings to make installation easier.

[Der Konig]

All this would tell you is that the pcv is working correctly and rms/crank seal are functioning correct? Nothing about vacuum leaks?

Just did mine. Also good. Same as old guy on same gauge.


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[NitroViper]

Need vacuum stats on the black top PCV if anyone has that.

[Smac770]

Need vacuum stats on the black top PCV if anyone has that.

I would expect it to measure .6 inHg, as speculated by a TSB that refers to it as a 20 mbar device.
What do you measure?

[NitroViper]

I would expect it to measure .6 inHg, as speculated by a TSB that refers to it as a 20 mbar device.
What do you measure?

Ill have to find a vacuum gauge. Im just interested what this $16 ebay PCV is compared to a $120 one. Im willing to try it tho for the sake of this cold start issue. The cold start thing is so random tho that it would take weeks to tell.

[old guy]

I would expect it to measure .6 inHg, as speculated by a TSB that refers to it as a 20 mbar device.
What do you measure?

What TSB would that be?

Thanks!

[Smac770]

What TSB would that be?

Thanks!

It was the one about problematic white caps from 2011-2014 coming with a bad diaphragm, the one that referred to that repair kit part number for the PCV diaphragm, 06H 198 542 A. I can't find it now. The process was "if you have the 20mbar PCV, stop now; if you have the white/clear PCV, proceed". Why they used the pressure spec for one and the color for the other, and why they used that reverse logic for relevance, who knows why they do some things.

[Smac770]

Audi seems inconsistent with terminology too. Take TSB 2030197 for the first gen 3.0T.

"Under certain driving conditions, internal engine pressure conditions in the 3.0 TFSI engine can negatively influence the rate of oil consumption. This can occur while the vehicle is operated in city driving conditions, for example: stop and go traffic with extended idle periods."
...
Production Solution
Crankcase pressure reduction starting with model year 2013.
...
If crankcase pressure regulating valve 06E103547H has already been installed or CAMPAIGN 24AP has been performed (both reduce crankcase pressure to 150mbar), perform steps 3–6 only.

At idle, it's vacuum, not pressure. But a negative pressure value would be normally interpreted as vacuum. Are we to just assume Audi can't be bothered with the concept of polarity? And they mean pressure was "higher, ie as on a counting line", and it was reduced to -150 mbar, which is a higher magnitude but a lower "number"? This is why technical writers are a bad thing.

[old guy]

It was the one about problematic white caps from 2011-2014 coming with a bad diaphragm, the one that referred to that repair kit part number for the PCV diaphragm, 06H 198 542 A. I can't find it now. The process was "if you have the 20mbar PCV, stop now; if you have the white/clear PCV, proceed". Why they used the pressure spec for one and the color for the other, and why they used that reverse logic for relevance, who knows why they do some things.

Thank you.

Very interesting information. So it seems to indicate that not only was there a control vacuum difference between the "black" and "white" configuration there was also a problem with the earlier "J" and "AE" white PCV valves that require a diaphragm replacement.

SMH.... Only Audi....

[Smac770]

I would say J, but not AE. J was current in Jan '14 (when I had my stage 1 done). The TSB referred to '11-'14, so AE was likely the solution (as noted by https://www.audizine.com/forum/showt...1#post14262469) with the fabric reinforced diaphragm (also noted in the TSB for the 4.0T regarding torn diaphragms). Whether or not that repair kit part number for the J's had a fabric reinforced diaphragm, don't know.

[clettngx]

I just checked mine. It's the J revision white top. Tested after getting one of those gauges. Looks to be okay. Thanks for the tip!

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[skifreak85353]

2014 allroad, original white top, AK revision, 95k miles. Thinking I should replace the PCV…?

[JLAllroad]

2014 allroad, original white top, AK revision, 95k miles. Thinking I should replace the PCV…?

Not exactly, I see anywhere from 15-22 depending on circumstances, ac no ac, coasting, gear/rpm, temp……my understanding is that too much vacuum is more a sign of a bad PCV than too little.


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[skifreak85353]

Gotcha. I thought spec was 2.5-3? If so, I’m way outside of that.