Changed my pcv and now have heavy vacuum at the oil cap

[Tankbrt5534]

I recently replaced the pcv, water, and thermostat on my 14' s4.

I did an oil change immediately afterwards and for some reason I decided to remove the oil cap while the car was running. There is a heavy vacuum on the oil cap. So here is my question is this actually normal? I have searched as much as I can and only get mixed answers. I know I did everything correctly and I dont suspect an oem pcv is d.o.a. there are no issue with the way the car runs or oil consumption or codes. Thank you all for any answers.

[JRYtheS4]

https://axleaddict.com/auto-repair/H...PCV-valve-test

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[BrokeBichB8]

Vacuum keeps the oil from leaking out of your seals. Its a good sign.

[ChiliS4]

This happened to me about 5,000 miles ago I did my PCV. It was actually tough to remove the cap with the engine running.

For what it’s worth, I’m either leaking or burning oil. It’s down about 0.5L over 5,000 miles.


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[rpalmer]

0.5L over 5,000 miles doesn't sound like any kind of a problem to me.

-RP

[Smac770]

The crankcase vacuum on the B8.5 3.0T should be 150 mbar (4.4 inHg) during idle. More than that, and there's probably a problem with the regulating valve in the PCV that meters the amount of intake manifold vacuum being passed to the crankcase at idle. Take the plug off the dipstick tube, put a vacuum gauge on it, measure the crankcase vacuum at idle. 150 mbar or around that, good. Not around that, not good.

The original CCBA (B8.0 3.0T) crankcase vacuum was much less, maybe 30 mbar. If a complaint of oil consumption was noted, the PCV was updated to the B8.5 version producing the 150 mbar vacuum level. https://static.nhtsa.gov/odi/tsbs/20...19987-9999.pdf