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997.2 Vacuum Level at Oil Filler Neck (let's build a data resource)

 
Old 10-02-2016, 01:35 PM
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EMC2
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Default 997.2 Vacuum Level at Oil Filler Neck (let's build a data resource)

A while back I replaced the AOS on my 997.2 3.6l. (DIY link here https://rennlist.com/forums/997-foru...rator-diy.html )

The car was running great and consuming an average amount of oil according to Porsche guidelines, so this was purely a preventative step. Although the car ran great before, it does actually feel a bit better/smoother after the AOS install (particularly at idle and in the lower rev range)

After researching the subject I realized there is really no reliable data online regarding what typical/expected vacuum levels should be on the 997.2. I bought the Porsche service manual and can't find it there, and even our helpful experts at Renntech are struggling to find the data.

It seems this value can be useful in diagnosing a faulty (or near faulty) AOS if exceptionally high vacuum exists, or possible poor ring sealing if very low vacuum exists. This could be better confirmed by the real experts. However I thought it could help us all if we had a reference source where members could post their readings.

I bought the following Manometer from Amazon, and checked it against a water tube manometer for accuracy before starting.
https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1

I bought a new filler cap for my car and used the old one to rig up the following using a brass fitting and plumbers tape to ensure it was air-tight:








09 997.2 C2 (72k miles) car fully warmed up / engine oil around 180 to 190 deg F
Reading Before AOS replacement = 13.9 in. H2O
Reading After AOS replacement = 17.5 in. H2O







The reason I found this interesting is that most advice regarding older variants of 911 (996 and 997.1 in particular) suggest you should be seeing about 5 in. H2O.

So I went ahead and measured my Panamera GTS and Cayenne S for comparison (with full understanding that they are very different engines, but figuring it would be an interesting comparison nonetheless).

The Panamera had 36in. H2O !!!
The Cayenne had 8in. H2O.
Both of the above cars also run beautifully with no oil consumption issues at all.

Please post your results here on your 997.2 values so we can build a reference for all who may be trying to diagnose issues, as the AOS subject comes up quite frequently.

thanks in advance

Last edited by EMC2; 01-06-2017 at 05:56 PM. Reason: added link to AOS DIY
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Old 10-07-2016, 02:21 PM
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Bruce In Philly
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2009 C2S 102.5K miles, MT, original AOS

Oil usage: Approx. 1 qt Mobil 1 0w-40 in 5K miles at 100K miles

Cold start: 18.8
After rev drop 14.3 (after about 1 mnt from cold start)
At full operating temp, 180 oil (full, top line), 13.1

To remove oil cap for my 2009:
1: Open and pull out spout
2: “close” oil cap (flip up like closed with spout out)
3: Gently pry, with thin screwdriver, at clip, do not force
4: Tube will not fall into engine, just push is back in and install new cap

The cap hinge pin has flattened sides that allow for easy removal from clips. Close the cap and the flattened sides align with clips and very easily comes off

Peace
Bruce in Philly

Last edited by Bruce In Philly; 10-08-2016 at 10:55 AM.
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Old 10-09-2016, 05:56 PM
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While I applaud your efforts, the reason that there is not a data resource on 997.2 cars is because the AOS has not proven to be a problem on the 9A1 engines as it was on the M96/97 engines.
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Old 10-09-2016, 07:20 PM
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You have pm
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Old 10-09-2016, 09:02 PM
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Originally Posted by phaphaphooey View Post
While I applaud your efforts, the reason that there is not a data resource on 997.2 cars is because the AOS has not proven to be a problem on the 9A1 engines as it was on the M96/97 engines.
Yes I realize that, however there have been 2 forum members (that I came across) who replaced their AOS on 997.2''s (one because Porsche said it was faulty and the other as part of a troubleshooting exercise, where it wasn't determined if it was really faulty).

The reality is that the diaphragm is something that will fail eventually even with the revised design.

There are also quite a few 997.2 owners with concerns about high oil consumption, and the AOS is one of those parts that can be a contributing factor.

The aim therefore, is to preemptively build a data resource for when these AOS failures do become more common as more cars get up in both mileage and age.

As mentioned, even the RennTech team could not find the recommended figure and the Porsche technicians Servive manual I purchased doesn't have it either.

Interestingly there are examples of other engines/manufacturers which list the pressure values clearly such as in the example below. (see top of pg 22)
http://www.natef.org/NATEF/media/NAT...-6-FSI-SSP.pdf
VW 3.6l FSI engine

Originally Posted by Dan GSR View Post
You have pm
PM replied.
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Old 10-13-2016, 08:35 PM
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On my car (09 C2 3.6L) with 74k miles, I got a reading of 13.6-13.7 at normal operating temperature.

Thanks
Rob
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Old 10-13-2016, 09:38 PM
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Thanks Bruce and Rob for posting your numbers.

I'm starting to wonder if the updated AOS I installed (p/n 9A1 107 040 02) uses a different membrane or spring to sustain a higher vacuum.
Note there were 2 prior versions of this part available ending in 00 and 01.

Is there anyone out there that has the new part and could share their measurements?
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Old 10-22-2016, 11:02 PM
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Dan GSR
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2009 C2 3.6
33,070 miles
16.1 inches of water

2011 C4S 3.8
52,142 miles
12.9 inches of water

both measured fully warmed up
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Old 11-02-2016, 07:53 PM
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2011 997.2 C2 3.6
Mileage: 16,007

I had oil (Mobile One 0W40) and oil filter kit changed 3 months ago.


COLD START: measurement started with 16.6 in. H2O then climbed to almost 19 in. H2O and started to drop again.

AFTER REV DROP (about a min from cold start): 13.5 in. H2O

FULLY WARMED UP: 11 in. H2O


Many thanks to "Bruce In Philly" for providing instructions to remove the cap. I used a flat screwdriver wrapped with electrical tape to remove the cap and used my thumbs to clip it back after the measurements. Just make sure to keep the cap in "closed" position while uncliping it and cliping it back.















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Old 11-03-2016, 10:14 AM
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Thanks for posting your results EC.
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Old 11-03-2016, 08:04 PM
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Originally Posted by EMC2 View Post
Thanks for posting your results EC.
Thank you for letting me borrow your manometer
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Old 11-08-2016, 12:17 AM
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Not much consistency in numbers
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Old 01-06-2017, 05:57 PM
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Updated original post to include link to AOS DIY.
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Old 05-04-2018, 03:37 PM
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2009 C4S - 72k miles - burns approximately 1qt of oil every 800 miles (confirmed minor bore scoring).
Measurements done at 725’ above sea level.

20.5” H2O directly after cranking while engine has high RPM.
16.7” H2O 60 seconds or so after cranking when RPMs drop to idle.
14.5” H2O after a drive with engine oil around 190 F.




Last edited by Mr_Skull; 06-06-2018 at 10:56 AM.
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Old 05-04-2018, 05:30 PM
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I found this in another thread and felt it was worth placing here.

Originally Posted by Flat6 Innovations View Post
....the other test that can be performed to test both ring seal, and the AOS is a manometer test. The DFI engine should test at 16" of water column, and can be slightly higher at sea level, and slightly lower at low elevations.
Unfortunately it doesn’t state if that’s after you crank the engine and wait for the idle to drop or if it’s after the engine and oil are at normal operating temperature.

Last edited by Mr_Skull; 05-20-2018 at 06:11 PM.
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