Oil Cap Suction
 

I'd like to see how many people have significant suction through their oil fill cap. My local Audi shop seemed baffled by the fact that I had such a large amount of suction in the system. Reason being is, if there is suction in the crank case it will be pulling on any seals in the block, potentially causing leaks or catastrophic failure down the line (their words, not mine).
They had a 2017 RS7 with 8k miles on it in the shop, and it required a similar amount of effort to pull the oil cap off.

If anyone has definitive info as to whether this is normal or not, please comment. Otherwise, please post your vehicle details, whether or not you've replaced the PCV valve, and if you have suction through the oil cap. Shouldn't take but 15 seconds to pop the hood and try and remove the oil cap with the engine running =).

I'll start with mine:
2013 A8L 4.0T
PCV replaced
Suction through oil cap

Hi Folks,

Resurrecting this thread as I have a similar question so if anyone can reply on if their oil filler cap is very difficult to remove due to high engine vacuum at idle - this would be greatly appreciated

Completely normal. High engine vacuum is very common on modern engines. It helps the low friction rings seal better.

Oil cap suction on '14 Q5 3.0
 

I tested mine and had a very strong vacuum pull on oil cap. Have a Q5 3.0. I was getting a static pcv regulator valve performance fault in OBDEleven. The car runs fine and there is no visible oil leaks. I just completed my 115k service myself and had not purchased the obdeleven until after I did the plugs, coils packs, air filter etc. Did you get any more feedback/answers?

I performed an oil change this weekend, via oil extraction method. My engine has 24,6XX miles on it, and there was strong suction on the oil cap when the engine was running. It definitely caught me off guard at first.

My D2 S8, with the 4.2 V8, didn't have the oil cap suction, but that engine was slightly less advance ; ) I hope my D4's engine is as reliable/bulletproof as my D2's engine with 144,XXX miles.

Hi, You will find several posts confirming the normal presence of vacuum in the engine crankcase however, the oil cap should be relatively easy to remove with the engine operating at idle so a partial vacuum will be present.
My experience : With the defective {new} eBay cheap oil separator I had installed this resulted in a very high vacuum present in the crankcase at idle speed, making the oil filler cap impossible to remove by hand, high oil consumption and an intermittent misfire.
When I replaced that defective oil separator with Febi the idle smoothed, no more intermittent misfire, and I can now remove the oil filler cap with the engine operating at idle. There is a slight vacuum present and this is normal. Hope this helps...

Oil cap suction
 

Thanks guys. I can take the cap off by hand. I just never did this with the engine running and decided to do so when I pulled the dipstick and it was experiencing suction. There's a TSB out there for the PCV valve/crankcase pressure. I'm going to call the dealer and see if I'm covered. If not, I'll likely replace the oil separator with genuine. Thanks again for your help.

Hello,

Was there ever a final determination here on oil filler suction? My 07 D3 5.2 will stumble and almost stall if I remove oil cap at idle. Rough idle with occasional misfire codes in general.

Thank You

Oil cap suction
 

According to two local audi shops and a few members here, suction is normal as it is a closed system. My A8 quattro has suction at idle when I remove oil fill cap and dipstick plug thingy. Runs , drives, and idles perfect with no codes. So I am going with the hope that this is a normal operating condition.

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Just following up...
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Normal crankcase vacuum, 105K miles -> https://tinyurl.com/2s7ma482
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Unmute the video.
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